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Comment by thaumaturgy | Hacker News Reader

I'm unaware of any good design guidelines for colorblindness. In general, I find hues of red/green and blue/purple/red difficult to distinguish. Green and blue are great! Greens/yellows/blues all work well. And, similar colors that aren't the same saturation are, sometimes, okay. And of course if the color isn't meant to signal important information -- like if it's just a flourish in a design -- then I'll never notice.

But the worst offenders are always maps with color gradients ranging from red to green.

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Ah, thank you for saying this. I'm in the middle of drafting a fairly complicated visualization for something I'm working on. I avoided red-green contrasts because that's the most common form of colourblindness, but I thought red-purple-blue would be distinguishable. I'll have to try out green-yellow-blue instead.

Obviously that won't work for all kinds of colour blindness either but I can't figure out a straightforward way of representing this particular thing without colour ... it's literally about a graph colouring problem. Patterns/textures maybe? But then the nodes would have to be larger than I'd like so that there's enough surface area in each node to recognize the pattern, and then it would become very crowded.

Super rough rule of thumb: 98% of colorblindness issues are “red and green do not contrast”, 2% are “green and blue do not contrast”. Orange and blue will contrast for pretty much everyone, that’s the safe and easy to remember bet.

For creating contrast in other ways: saturation and brightness are unaffected by colorblindness and you can create contrast with them.

Simple rule of thumb in most cases is if you can convert it to grayscale and still tell it apart your colorblind users can too.

Barring that as a red-green colorblind person, yes red-green contrast is the worst, but way more common are colors that are only different by their red or green strength (especially red). The two most common by far being pink becomes white and purple becomes blue.

Your green-yellow-blue suggestion is actually making the same mistake as red-purple-blue just using green as the fade instead of red. Having said that in my experience red-green colorblindness is actually RED-green colorblindness. So, I would much prefer a green-yellow-blue interface to a red-purple-blue one. As I am much more sensitive to green than red.

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