Comment by TeMPOraL | Hacker News Reader

Comment by TeMPOraL | Hacker News Reader

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> Having three primary colors never made much sense to me either, but that could just be my own ignorance.

Tree primary colors thing seems to be mostly ignorance of the educators teaching that stuff to children. There are no absolute "primary colors" - basically, you can pick any colors at random and use them as a base for linear combinations; the set of colors you can express as such linear combinations form a color space defined by those base colors you picked. Red, green and yellow are a common historical picks, RGB is more common now because that's what is put on the computer screen, but CMY form a color space too.

C.f.: https://en.wikipedia.org/wiki/Primary_color#/media/File:CIE1... - the triangle inside is the color (sub)space of RGB overlayed on CIE 1931 color space (https://en.wikipedia.org/wiki/CIE_1931_color_space).

Source: I educated myself when I got asked by a local drunk to resolve a bet between him and (presumably) another local drunk while I was shopping in a local grocery store. Those two got into a bet over whether RGB or RGY are primary colors.

I always understood it as RGB being additive -- each color directly stimulates a given color cone in the eye. Whereas process colors (CMYK) are subtractive, because they are a tint. White light hits the paper, but each color (Cyan, Magenta, or Yellow) takes out a certain RGB color leaving the remaining two colors to reflect off the paper. For example, Cyan is a filter for Red, leaving Green and Blue to reflect.

I'd say it's a property of the medium, not of the colors. Computer screens blend additively because you emit a mix of light waves; pigments blend substractively because they are filtering out wavelengths from incoming white light. Color spaces and "primary colors" are orthogonal to that.

RBY is what is commonly taught as primary bases in school, due to color compositions and the ease of expressing it through mixing pigments.

R + B = Purple R + Y = Orange B + Y = Green

Right, I probably meant RBY not RGY; I wrote from memory, and meant the one most commonly taught in primary schools in Europe.

So who won, based on your exposition? Or was it a draw?

I left that for the two to settle between themselves. I just explained the thing to the guy that asked me first. He was on the RGB side, having shown me a picture similar to this one[0] on his mobile phone. My guess is that he ended up claiming victory, because when I tried to explain the details of the problem, he was going all "so this means RGB can be considered primary colors, right?". I never met the other guy.

[0] - https://en.wikipedia.org/wiki/RGB_color_model#/media/File:Ad...

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