Tetrachromats: people who see colors invisible to most of us (2014)
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She also sometimes see colors in her dreams that are outside of a pallet humans see in real life, but after she wakes up she can't describe them. It's not one color or one hue, there are several colors that she can only experience in her dreams.
Sounds like she is describing imaginary or impossible colors.
Image search "color illusion": https://duckduckgo.com/?q=optical+color+illusion&t=ffab&atb=...
Or see (literally) "Benham's top" where a black-and-white pattern on a spinning disk induces the perception of color. https://en.wikipedia.org/wiki/Benham%27s_top
I see slightly different colors out of each eye, with no way of knowing which eye is correct.
Neither eye is correct: color is subjective.
"Who is the master who makes the grass green?"
It's a deep question.
With psychedelics, I saw colors that I'd never seen in reality. But that's just color illusion on steroids.
What interesting, though, is that I saw patterns in objects that normally seemed ~uniform in color. So maybe "software tweaks" can mitigate hardware limitations.
It seems to me that when everything looks the same from birth on (excepting perhaps focus. ;) ) then it is difficult to compare what one sees with what others see.
I also wonder if some colored LEDs tend to be "worst case" as they may be monochromatic and if the eye is not sensitive to that particular wavelength, it will not be visible as color.
Actually... I also wonder about how a wide gamut of colors can be represented by relative intensity of three primary colors: red, green and blue. I would expect the emitters in, for example, an LCD screen to emit light at specific frequencies. How can any combination of three frequencies represent what must be a broad rage of frequencies that form any given color in the world around us.
How colorblind you are -- or maybe in what way -- determines which color combinations you can distinguish characters for. That's horrible, I know, but I'm tired.
I suppose it depends on what mutation(s) you carry. And probably other factors that affect penetrance.
So "somewhat" was the diagnosis, not my experience.
But I have known other red/green colorblind people. And I can distinguish reddish vs greenish colors better than some. But worse than others.
http://www.dict.org/bin/Dict?Form=Dict2&Database=*&Query=col...
Freedict gives:
That aspect of things that is caused by differing qualities of the light reflected or emitted by them, definable in terms of the observer or of the light
https://www.thefreedictionary.com/color
That is, colour is a perception, dependent on the observer. Agreed-on colours being those on which typical observers share common experience, is correct.
Wavelengths, pigmentation, and diffraction effects (which give rise to colour in observers) are phenomena.
The terms quale and qualia suggested by @codebolt are indeed quite useful.
(Language itself is shared agreement among symbolic references, given context.)
Tetrachromats could plausibly see more nonspectral colors by activating their extra color receptor and one of the other ones. There would be no exact equivalent in trichromatic vision.
It depends on what their brains decide to do with it- maybe they would just land on an existing color in between. But there's no reason it has to.
So these colors are something that tetrachromats could maybe see while awake, but usually with lots of other colors mixed in. Asleep, maybe the brain starts to play with them and generates pure versions of them. Trichromats wouldn't be very likely to have these dreams because their brains don't have experience of tetrachromat nonspectral colors at all.
I imagine in school the teacher tells the poor girl: Mix the blue and yellow colors to get green, and the girl doesn't understand because she has a lot more complex color model than the teacher.
We see magenta as a separate color because we can distinguish it from green- it's not green, because Red and Blue don't activate our green cones. But we can't distinguish between spectral yellow and R+G because there's no yellow cone: the activations of all our cones are more or less identical in both cases.
If you have a yellow cone, you'd conceivably be able to distinguish between both kinds of yellow: redgreen and yellow could look as different as green and redblue do. I'm not sure how that would look as a "wheel", perhaps a figure-eight with the crossing at yellow.
Whereas a hypothetical tetrachromat with an additional cone type that activates to the yellow wavelength, will have obviously different activations of their cones for the "wavelength of yellow" and "wavelengths of red and green mixed". And hence experience them as different colors.
I'm not familiar enough with the different definitions of color spaces to define how to model this. You could easily define it as a four-dimensional RGBY color space, but to my understanding the other color spaces are defined because they have better properties for combining different colors, or playing better with interpolation between colors.
It would be a challenge to come up with a good four-dimensional color space that is a useful artistic and visual tool, given that there are very few people around to evaluate it! And also because all computer monitors are trichromatic, so it'd be a job in itself to set up a test system.
I wish someone in the interview had asked some of these people how they experience photos on computers!
Tetrachromatic colors could be placed in a tetrahedron, defining a space and being approximated as a sphere. A perceptually uniform representation would probably be curved on the three edges that agree with the spectrum and flat on the three that don't. Green is still probably the biggest. Then you'd add luminance as a fourth dimension because it's still rods.
With tetrachromats we get a four-dimensional space of color. So we need something like RGBX or a two-dimensional hue value like for example H1,H2,S,V. That's what I meant with a second hue circle orthogonal to the one we already know.
What we see as yellow is for the tetrachromat a whole second hue circle varying in the value of second hue.
An example: Yellow is a point on the first hue circle. For the tetrachromat these colors are different, but boring yellow for us:
- pure yellow
- mixture of red and green
- mixture of pure yellow, red and green
In other words, what we see as yellow is a whole dimension of different colors for tetrachromats.
Also, if you mix R+B, that's magenta, and if you start mixing in blue it will turn white or gray. But if you can see yellow, RYB would look different from R+a little g+B, which is what RYB would look for trichromats, I think.
This is honestly one of the saddest parts of human society. Some people, including those in positions of authority, either don't understand or outright reject the notion that different people perceive the world differently.
In secondary school I argued along the lines you describe, that you can mix three colours in a circle, and then a fourth around the circumference mixes only with at most two of the others - and in terms of the FCT is then a 'barrier' allowing re-use of the first three.
That's quite off-topic, but you suddenly jolted my memory of it. More on-topic, being colour-blind (never told which type and I can't work it out either) I find conversations about colours frustrating, and very strange to wonder if we see anything alike at all, or just learn to call the same physical thing alike despite perceiving it perhaps very differently.
Proving some maps can't be colored with three colors is easy, you only need to find one and enumerate all the three-colorings and find none of them work.
It's not really a theorem about colors though, they're just labels.
Re proving any, I replied to a sibling comment. What I was imagining was the inverse - proving that you can't construct one that requires a fifth.
I recognize that this comment includes jargon, but I assume you'll Google it. I'd include diagrams but HN doesn't support them.
But, I understand and trust the mapping of the problem to a graph, so perhaps if I see why the problem is hard on a graph that should be enough for me.
But my reasoning was along the lines (but now in my newfound terminology) of:
K1 - trivially 1 colour needed. K2 - 2.
If we add another region on the map, we either have K3 or K1,2. In the latter case the third region/vertex need only be different to the one it touches, but K3 clearly needs 3 colours.
Adding the fourth region is similar, and again K4 clearly needs 4.
The fifth region touches at most 3 others, since K5 is non-planar. Thus, it can take the colour of the untouched region.
That's not very formal, but why isn't proof by induction easy from there? i.e. if we can't build a map that ever requires a fifth colour, then it can't be that there exists a map which requires more than four?
* It's easy starting from the end, just put one colour in the middle, then alternate second/third colours around the edge until you get back to the start and have to add a fourth. From construction, the worst case is from K1,2 then adding another for K1,3 at which point we need four colours already, but when we add two more on what will be the C5# around they each only connect to one each side and the center. In adding each one you can simply use the colour one hop over on the circumference.
# Since the center of K1,3 must be the center of the final C5-plus-thing, as it already had 3 spokes.
It's just that the C₅-plus-thing requires four colors, even though it doesn't contain any K₄ induced subgraphs. So we could imagine that there might be some larger planar graph that requires 5 colors without containing K₅. As it turns out, there isn't, but that's the thing that's hard to prove.
You could put them in front of light source that generated pure wavelengths designed to selectively activate their extra cone and ask what they see when you start mixing pure blue or green into it. Maybe they'd recognize those colors from their dreams, maybe not. I don't know. But it's a mechanism that would explain how tetrachromats might dream colors that trichromats don't.
We don't see bright, "pure" magenta very much, and when we do it's usually because we've engineered it. Nobody is engineering pigments for tetrachromats to enjoy.
If I'm right, people who are nearly (but not entirely) colorblind (anomalous trichromats) due to a shifted cone would likewise be able to dream in colors they are capable of seeing only dimly while awake, whereas dichromats wouldn't.
The trick to impossible colors is recognizing that our existing receptor spectra overlap. It's not possible to get "100% red" in the sense of only the "red" cone cells firing and none of the "blue" or "green" ones, because those other cells are going to fire at some small rate for the same frequencies.
But our brain can certainly receive such a color even if our eyes don't produce it, so in some sense we "understand" it as a color even if we'll never see it outside a laboratory or hallucination.
There are separately colors which we are wired to hypothetically receive, as you point out (and I find interesting) - IE, if you replace the eye with some sort of artificial replacement, then such a signal could get received by the brain, but with the current sensors it is impossible (also, I suppose a colorblind person could receive such a signal as 100% red without the other colors).
There's also the possibility during a dream of creating objects or sensations that are not physically possible. For instance, I've had dreams where I had a form of telekinesis, and obviously there's no sort of brain wiring to manipulate physical objects outside of the normal motor functions. Still, it made sense in the dream - and it's not like I could describe how I did it, and it's not because the hardware exists but the sensor doesn't.
Although - you could argue that there's a layer of abstraction in the brain of such things in the brain - for instance, when I'm typing these words I don't actually ever have any conscious awareness of my finger motions. I don't even think about the act of typing at all; only the words. So, thinking about it, the brain does have an idea of manipulating objects outside of a need for muscles to do it.
I would think for a tetrachromat the abstract sensation of seeing colors you can't describe to others is itself a familiar one, and that feeling itself is something you might encounter in dreams. My dreams tend to start with a feeling, and then build a context for it.
Tl;dr - dreams are weird.
Strange to think there are people who can perceive two orders of magnitude more colour than me. Damn.
Think something like an RGB lamp but with more colors/wavelengths, and adapted to her particular spectral response.
Having built a similar kind of lamp myself, I have to say it was quite wild even for a boring old trichromat as me!
Maybe those colours are what I would see if I had properly functioning cones, or even a fourth cone variant. Or maybe they're just a symptom of wider brain dysfunction due to the psychedelic drugs. Hard to know...
It makes me fairly proficient at driving, dodging moving obstacles while doing any physical activiy, and fast-paced games (like FPS) - even if the trade off is that I occasionally killed teammates because I couldn't see the color differences between players at times.
Everything has it's pros and cones (pun :D)
This type of pattern matching is frequently how I go about navigating the world.
Of course I envy her, but I mostly just happy that she can experience some aspects of our world better than most other people. It's like with talents: the fact that someone has a particular talent or skill that you lack doesn't make you hate this person. Instead you ask them to show it off, they do, you "Oo-ooh!" and "Aa-aah!", they feel really good about themselves and you're both happy.
Sometimes she is sad I can't appreciate something she sees, but we don't dwell on it. She would often describe the shape or a pattern she sees and I try to picture it and say something like "Oh that's neat!".
Also, there are some clothing items I never combine, and I always ask her for advice when I select my cloths, or colors for my presentation or charts.
Colors are very cool. I wish we could have some kind of tech that would allow us to see colors like some birds or aquatic species do. These days there are glasses for colorblind people to give them some extended color perception, so the tech is making some baby steps.
It turns out that many color-blind people have the normal distribution of cones, but the spectral response is similar enough that the brain can't differentiate. By putting an optical notch filter in the overlap region, the difference is accentuated and the brain starts picking it up normally.
You can practice by surrounding yourself with people better than you. Play games with people better than you. Find mentors.
Grow as a person so you love yourself rather than envy others. Recognize that almost everyone has something you don't. Better than you at something.
Reflect on the great things about yourself. Remember who you are. Where you started.
Be good. Be true to yourself. Develop your moral code. Treat all with respect and love. Including you with all your imperfections.
But by 2010, [Jordan] had found a subject who perfectly acted the part of a tetrachromat. Jordan’s “acid test” involved coloured discs showing different mixtures of pigment, such as a green made of yellow and blue. The mixtures were too subtle for most people to notice: almost all people would see the same shade of olive green, but each combination should give out a subtly different spectrum of light that would be perceptible to someone with a fourth cone. Sure enough, Jordan’s subject was able to differentiate between the different mixtures each time. “When you ask them to discriminate between the two mixtures, a tetrachromat can do it very quickly. They don’t hesitate,” says Jordan.
Science has a method for cutting through speculation - in this case, it is a variant of the Ishihara test.
I'd use a 2-panel diagram. On each round, the panels are assigned random colors. The subject is asked "are the panels same, or different?" Some proportion of the time, they're identical. If they just mash "different" every time, you'll see that in the data and you'd reject those subjects -- or accumulate those false guesses into an uncertainty measure. If they hit 'same' on different colors... make a graph with edges between those colors. Some time after the graph is connected, try and find a minimum vertex cover. The order if that vertex cover should be a reasonable estimate of the number of colors a person can see.
I have such a pair, but have to say it's not very exciting; there's not that much metamerism in the real world.
Where did you get your pair? What filters did they have?
[1] https://bugzilla.mozilla.org/show_bug.cgi?id=627771 (note the linked example is from 9 years ago and the -moz-linear-gradient CSS attributes no longer work.)
The 24 bits are 3x8. To accommodate tetrachromats, you'd go to 4x8, not 3x10.
The idea of accomodating tetrachromats is certainly quite interesting, but it doesn't appear they all have a fourth rod that responds to the same frequency distribution, so 4x8 would only work for individual people, not tetrachromats at large?
[1] https://en.wikipedia.org/wiki/Color_depth#Deep_color_(30/36/...
Wait, that didn't make sense to you as a trichromat?
Neither does your suggestion to a tetrachromat. For them color is a four dimensional space (tetrachromat literally means "four-colorist"). The RGB cube becomes a RXGB hypercube. You can't emulate X with RGB like you can't emulate green with red and blue.
As someone who watches a lot of cartoons, I'm grateful. I'm also grateful for how smooth TV has gotten in the HD era. I was using a neural net to restore standard def TV and make it look like proper HD fooling people around me, but the frame rate difference due to deinterlacing is a giveaway.
Also, in the 90s most anime, for example, was 24 fps, where modern day anime is 30fps or higher. This difference is noticeable as well.
One optician panicked so much at what she said they referred her to the hospital in case she was having a stroke! And that's when we discovered what she can do. I just thought she was good at picking clothes that went together well.
Good for her, but I doubt this is because she can "see colors nobody else can". If that was the case, she would most likely be worse at picking colors which (to the average eye) goes together well. Maybe she just have good taste?
If you pick points that are close together in four-dimensional space (to make a simplistic analogy) they'll continue to be "close" in a topological sense under any linear projection to three-dimensional space. Or for a different analogy, if objects group together under a filtration, they'll continue to group together under a coarsening of that filtration.
But the moonlight painting gives it away. Most people don't see any colours under low light, and being able to see and paint a colourful scene under those conditions is a unique ability.
Of course it could be imagination, but it doesn't look like it. The tree and the moonlight paintings have similar colours to the ones you'd see if you took a photo of a scene and turned up the saturation in Photoshop, with a few extra shades. It's a surprisingly literal and unimaginative form of exaggeration, and it's not how most painters distort colour for effect. So I'm more inclined to think it's a perceptual feature, not a creative choice.
- It should be easier for them to paint highly photo-realistic scenes.
- They should struggle to find the right colors to buy in the shop.
- They should be frustrated with mixing colors because they could never get the color right as they see it.
In addition, painting photo-realistically is more about edges and angles than colors.
Just imagine if the pigment selection were designed by a color-blind person.
For example, if you hold up your hand to shield your eyes from the sun, that's a pretty challenging situation to paint. But the way the after images of the sunlight interact with the silhouette of the hand suggested to me that the idea could be conveyed by painting a shimmering primary colour halo around the hand. And sure enough, Antico's paintings look much like what I had in mind.
Let me explain: our eyes perceive RGB, but we don't in consciousness -- the RGB is mapped somewhere, long before consciousness, further in the brain to more of a perceptual RYGB -- a two-dimensional space of warm/cold (RY/GB) against "lighter/darker" for lack of a better term (YG/RB). See [1] for more info. Psychologically yellow functions as a primary color even though we don't have a rod for it. (In reality it's much more complicated than this, since we perceive saturation, brightness, etc. but this is a valid simplification for current purposes.)
So it's entirely possible that tetrachromats map their four rods to the same RYGB box the rest of us perceive as qualia, only with a different mapping. Then, they can still distinguish between colors everyone else sees as the same (because different spectra), but they'll still perceive them as the same color qualia the rest of us perceive -- colors in the world will just be mapped slightly differently. The closest (but imperfect) analogy I can think of is wearing polarized glasses -- same color gamut, but certain things "compare" differently now.
Or, does tetrachromacy somehow also change the perceived-qualia RYGB model itself? So there's, say, a 3rd axis beyond warm/cold and "lighter/darker"? Or the span of the two axes somehow becomes wider to accomodate more information? Or something else?
Hope this is clear. Perhaps it could be tested psychologically, though -- simply by asking participants to describe the colors they see qualitatively, to see if the words they use in color comparisons (e.g. warmer/colder) are the same as those used by the rest of us... or if there's any new "feeling" component involved.
[1] https://en.wikipedia.org/wiki/Opponent_process - "...the cells were widely called opponent colour cells, Red-Green and Yellow-Blue. Over the next three decades, spectrally opposed cells continued to be reported in primate retina and LGN."
To answer the question, as qualia cannot be compared from person to person, there is in principle no way to show that they differ (or are the same) objectively. A sort of relative comparison of qualia within an individual (as you propose) will also not get you there, as it may be that the individual is simply more sensitive to changes along the gradient, not that they are experiencing a new color, and that's assuming we are able to use an objective comparison scale which we aren't.
Here's another way of looking at it: psychologically, we don't perceive yellow as a mixture of red and green, the way we perceive purple as a mixture of red and blue. Yellow isn't "perceived" as a mixture of anything in our minds -- it's perceived as primary. If you say "it's kind of a reddish-green", nobody is going to think, "oh you mean yellow!" While orange is perceived as a mixture of red and yellow, for example.
Remember, I'm not talking about what's happening physically with wavelengths -- I'm talking about psychological perception of colors.
The L cone is actually most sensitive to the yellow wavelengths.
There is an African tribe that can see more greens and browns, due to their genetics and it has been proven for them.
Don't quote me on this, but I believe as a whole qualia has been proven. That is, we all do experience the world differently, but we can both point at the same thing and give it a same name. Words like 'red' are just pointers to the colors we see, and everyone sees it differently. This, ofc, doesn't guarentee we can see more or less levels of detail, just that we what we do see can be different.
You can enjoy reading: https://en.wikipedia.org/wiki/Qualia
If they did this then wouldn't they necessarily also confuse some colours that trichromats can distinguish?
That wouldn't prove, but it would strongly suggest, that they're seeing the same qualia as the rest of us in the end, just mapped differently. Particularly if we could find "symmetries" -- i.e. for each area of new distinction they see, there's a corresponding area of distinction that collapses.
I do not know if subsequent technologies like OLED, Quantum dots, HDF capture much of the color increase of the six channel system.
I do not know if the six color system could be used to quantify tetrachromacy.
I'm skeptical of the articles claim that the painting gives us any insight in how a tetrachromat perceive the world. This is just like claiming a color blind person would be able to perceive full-color vision by looking at a painting. Never mind that tetrachromat painters would have real difficulty finding the necessary color pigments to reproduce what they see.
Presumably like trichromats experience Kinemacolor (https://en.wikipedia.org/wiki/Kinemacolor).
Only the real world does.
If you're not able to differentiate between colors you're not able to see those colors.
Hell, your argument can be stretched to stating that there's no difference between monochromatic and trichromatic vision as long as the covered light spectrum is the same.
That’s patent nonsense.
Some are, some aren't. Anomalous trichromacy (where one cone type is shifted) is still considered color blindness.
If so, that would be an interesting way for a tetrachomatic magician with a mentalism act to have their assistant pass them information. In particular, it would almost certainly work to fool Penn & Teller on their show "Fool Us" [1], where it often comes down to whether or not the mentalist can find a way to pass information that Penn & Teller can't spot.
To my mild surprise, 10 minutes googling did not find any description of how it works.
It's interesting to notice how designing screens to use the RGB colors is very limiting for those people.
Imagine living in a world where 94% of people have the same form of color blindness and you don't.
People would randomly mix e.g. blue and green in every place and ignore your comments with a smirk.
As the article notes, Jordan & al spent 20 years researching tetrachromacy before they found a functionally tetrachromat individual.
Wouldn't it be really confusing?
Are there lines of painting and art supplies specifically for tetrachromats?
(Being a little sloppy with sex stuff here. Not all women have two x’s, women can be colorblind too, etc.)
• Two of our usually-three cones are specified on the X chromosome
• When one of a woman’s X’s specifies an anomalous cone she ends up with a 4th, anomalous type of cone.
• This happens ~14% of the time for women.
• That’s about the same percent as color blindness in men.
• That’s not a coincidence. Because color blindness comes from one of these women’s sons getting that anomalous 4th come instead of a typical 3rd cone. This anomalous cone tends to overlap more with one of the other cones in its range of perceived frequencies, which is what causes color blindness.
• But only a small percentage (not sure what percent yet?) of these women with 4 different cones actually seem to be able to perceive more colors
• that’s because the 4th, anomalous cone might basically fully overlap with one of the typical ones in its perceived frequency range, so it doesn’t really give the brain any additional info
• one question I have: so it seems like not all these anomalous cones are the same. Is there a fixed number of types? Or is it more of a spectrum? Further, are /all/ cones on a variable spectrum? Or is almost everyone’s blue cone exactly the same?
• this was interesting: colorblind men actually have a set of colors they can distinguish that people with normal color vision can’t (the article explains why)
• in this study they found colorblind men (but by looking at unusual things they /could/ see, not things they couldn’t? Not sure) and then tested their mothers to see if they could see extra colors.
• Most of them couldn’t. One of them could. The study was only like 9 people? Safe to say /all/ of these women had 4 types of cones, even though only one of them had a sufficiently non-overlapping fourth one to get some benefit?
• As a colorblind man, I’ve never noticed an ability to distinguish colors others can’t. Only the opposite.
• it’s intellectually neat to know that’s possible, even if it doesn’t tend to “come up” in everyday life.
• It souuuunnndssss like the amount of extra color vision that these tetrachromats get is only the same as the extra color vision /I/ get—that same “theoretically there, but doesn’t seem to come up in everyday life” thing. That’s a little disappointing—I though tetrachromacy was more kooky.
I get a stronger blue channel from one eye than the other. So I'm quite sure that there is variability, it's a matter of degree. Also, research into language and culture shows that the brain is heavily influenced by colour as well. Some cultures have difficulty seeing differing shades of blue or green that westerners think are trivial.
Alternatively take photos with a normal camera and then with the same camera with a coloured filter. Choose the filter so that it only partially interferes with each colour of sensor (magenta should work well). Then the two images have six independent colour channels between them.
Sensors, displays, software.
Unicode encompasses vast numbers of characters, wouldn’t an update to colour science and displays be in order?
Since they can perceive more colors, it's never an accessibility issue, so it's far more important to accommodate dichromats, and that's already very hard because we can't tell how a person with a different set of cones would perceive a particular color just by looking at it.
Also, we already have a color model that can't reproduce true cyan as perceived by "regular" trichromats, and so far that hasn't been a real issue.
Is the same true for magenta as well? Is it a problem to convert between RGB and CMYK?
Would really like to have a comparison between a monitor that can display those colors now. Apparently there are some more expensive monitors that can display an extended palette.
As the article and the name of the condition state, there is a physical difference in the optic system that causes this condition. No subjective analysis is needed.
(Though I can't quite agree with Jackson that qualia refutes physicalism.)
Stylized facts:
- Brown is dark yellow.
- Yellow is a mixture of red and green.
If I opened your brain and swapped your red with blue, you would not notice.
That said, our shared physiology and biology as humans makes my default assumption that red looks about the same to me as to anyone else. Unless they're colourblind or tetrachromats, of course.
But in rare cases extra cone has a quite unique activation curve and allows to differentiate mixes of wavelengths that are perceived as the same color by most people.
More in-depth explanations: https://theneurosphere.com/2015/12/17/the-mystery-of-tetrach...
You can't replicate RGB with just R an B, even if you crank up the resolution.
Assuming that the cones of different frequency range have approximately the same degree of sensitivity, I'd be thinking that the number is about n^(4/3) where n is the number of colours perceivable by trichromats.
But even if that's true - which I doubt - the additional colours are in unlikely to have a useful distribution, and will be centered around the frequency response curve of the fourth cone (I believe it's generally in the yellow spectrum; somewhere between red and green).
It doesn't require any pop-psychological explanation - you can easily make an electronic device which detect the color purple. It just needs to be sensitive to more than a single wavelength.
> Whilst we can see violet and blue next to each other, there's no purple. Because purple doesn't exist.
Back in reality, "purple" and "violet" are synonymous.
The article also makes the completely unsupported assumption that the color you "should" be seeing when you look at a mixture of wavelengths is the color of the average wavelength of that mixture. That's how it decides that purple "should be" green. But that's nonsense.
> When you see red and green for example, the L and M cones both fire, and your brain interprets the result as something near both. And what's near both is yellow. So even though there's no yellow light entering your eye, your brain imagines the result as yellow, because both cones are being stimulated in similar amounts.
This gets the causality backwards. When you see red and green, your L and M cones both fire. And you interpret that as yellow, because yellow is what you perceive for that pattern of cone activation. To the brain, cone activation patterns are all there is. The question "what single wavelength would best approximate this activation pattern" is not even part of the model the brain is working with. But, obviously, if there is a single wavelength that approximates the activation pattern of a mixture, you'll perceive those two things as being similarly colored. Is it necessary for the single wavelength to be the arithmetic average of the wavelengths in the mixture? No.
Except when they’re not. People who have to think and talk about color on a regular basis, such as artists, sort colors into much more detail than people who don’t.
Have a look at the Wikipedia pages for purple (https://en.wikipedia.org/wiki/Purple) and violet (https://en.wikipedia.org/wiki/Violet_(color)). The image examples given for purple range widely, from a photo of some grapes I would call more blue than purple, to a dress that I would call magenta at best. And a color swatch that is somewhere in the middle of that range.
Meanwhile the page for violet leads with a specific wavelength, and a set of photos that are all very close to the swatch above them. This particular color could fit into the range of colors given as examples of “purple”, towards the bluish end of the range.
No, when you see purple you are not seeing something your brain "thinks should be green".
It's true that purple is a non-spectral colour. The rest of what that article says about purple is nonsense. (Perhaps motivated by the analogy they want to make with what they say about "customer experiences"?)