Whenever I need colors for a chart, I type "12 bit" in my address bar and pray my browser hasn't forgotten the URL: https://iamkate.com/data/12-bit-rainbow/
I usually do very simple charts, using maybe 2 or 3 colors, and with this palette I feel the results are typically very pleasing, whichever colors I end up selecting.
Is there another 12-color palette that allows you to easily distinguish between every color? If so, I'd love to see it.
I'd also appreciate if anyone who happens to read this who has a different variety of colorblindness - or who finds color palettes inaccessible for any reason - could share what colors in the 12-bit palette and any others that are suggested in this thread are problematic and why, that'd be awesome :)
My initial instinct is that finding 12 colors that are visually distinguishable for all users is likely impossible. That being the case, the ideal solution IMO is likely something like providing a dynamic option to change the palette (or even the representation!) and then choosing a default that the author is happy with.
Without going to lightness extremes, I agree that this likely isn't possible, at least when trying to accommodate all three types of dichromacy and for small color patch sizes (like those typically used for line and scatter plots). For example, you could take the 10-color accessible palette from work I've published [1] and add black and bright yellow to get twelve colors, but the lightness extremes of adding these colors would result in significantly-different visual weights. Based on a validation survey I conducted, I think even ten colors is pushing the limit of what's reasonable when lightness extremes aren't used.
> could share what colors in the 12-bit palette...are problematic
#9d5 and #4d8 is the color pair I find particularly problematic.
This is far from my area of expertise, but I’ve always been interested in accessibility on the web in particular.
Thank you for responding, I’ll probably be in touch :)
[0]: https://observablehq.com/@tomshanley/cheysson-color-palettes
If so... wow. That's not good at all; it's almost as hard to distinguish the minimum value from the maximum value as it is the two in the center.
Color-vision deficiency simulations collapse colors along the confusion lines, but this can be done multiple ways. These different mapping will all look the same (and identical to the original) to a dichromat but will appear different, with different perceptual differences between colors, to a color-normal individual. Simulating in a way that accurately portrays perceived color distances is still an open research problem.