I've got mild red-green colorblindness (less severe than the author's); this article is great, and goes into much more detail than I knew beforehand. If I could add some suggestions to the author's at the end:
* First, if you have the option of using one or the other, do so. Like, you can use red, blue, yellow, purple, and black for lines on a graph before you even need to find an additional color like green.
* Second, highly saturated ("computer" red/green) are easy to distinguish (for me, anyway, and it sounds like the author as well). So they're preferable to less saturated versions of red and green, if you need to use both.
For me, the most difficult reds and greens to distinguish are in the pastel range.
* Additionally, if you're designing UI for a program (game or whatever) with colorblindness options, PLEASE do not label the options with the medical names only ("deuteranopia", "protanopia", "tritanopia"). I don't know what the latin word for the medical condition of red-green colorblind is, I just know I have the relatively common kind of red-green colorblindness. I'd guess most people who aren't doctors are in a similar boat. Labels that include the color-distinction difficulty and relative commonality would be most useful to me, e.g., "red-green (MOST COMMON — deuteranopia)", "red-green (LESS COMMON — protanopia)", and "blue-yellow (EXTREMELY RARE — tritanopia)".
How about this for selecting. Colour scheme: just display a colourblind was test and ask the user to select the one they can or can't read. Then you don't have to rely on them knowing what the different types are at all.
To add to your suggestions: avoid referring to colors on a chart by name. While it may be able to identify the difference between two colors (e.g. by intensity), it may not be possible to identify the color. In my case, identifying blue and purple are frequently difficult. Presumably this is because purple is a mixture of blue and red.
The issue isn't with referring to colors on a chart by name but with using a color name as the sole identifier. Referring to parts of a chart by color is fine, and provides additional information, as long as a line style or shape identifier is also used, e.g., the "blue solid line" and the "orange dashed line" in the case of a line plot or the "blue circles" and the "orange squares" in the case of a scatter plot. Ideally, I think color swatches should also be included when referring to colors, so it isn't necessary to match the name to the color [1].
Yes, using multiple identifiers would work as well.
The use of colour swatches is interesting, though I would add that it should use a standard palette of colours to ensure that there is also differentiation based upon intensity (which would also help in the grey scale printout example).
> First, if you have the option of using one or the other, do so. Like, you can use red, blue, yellow, purple, and black for lines on a graph before you even need to find an additional color like green.
I don't see this advice getting much uptake.
First, green isn't a second thought for people with normal vision. It's a first thought. I can understand how this wouldn't be true if, to you, it didn't exist.
Second, the color space without green is harder to draw contrasts in than the color space with green.
Third, a friend of mine with red/green colorblindness always complained that he couldn't tell the difference between blue ("rare") and purple ("epic") items in World of Warcraft. (WoW has since solved this problem by throwing out the concept of item quality entirely, but the colors are still there anyway.)
So you're advising that people should make a quite unnatural choice, which will markedly reduce usability for almost everyone, but which won't actually solve the problem for the colorblind. It's just not a move that makes sense.
> Third, a friend of mine with red/green colorblindness always complained that he couldn't tell the difference between blue ("rare") and purple ("epic") items in World of Warcraft.
I call things that are apparently clearly blue “purple” a lot–I assume some sort of overcompensation of some sort. It’s strange how we adapt, isn’t it?
* First, if you have the option of using one or the other, do so. Like, you can use red, blue, yellow, purple, and black for lines on a graph before you even need to find an additional color like green.
* Second, highly saturated ("computer" red/green) are easy to distinguish (for me, anyway, and it sounds like the author as well). So they're preferable to less saturated versions of red and green, if you need to use both.
For me, the most difficult reds and greens to distinguish are in the pastel range.
* Additionally, if you're designing UI for a program (game or whatever) with colorblindness options, PLEASE do not label the options with the medical names only ("deuteranopia", "protanopia", "tritanopia"). I don't know what the latin word for the medical condition of red-green colorblind is, I just know I have the relatively common kind of red-green colorblindness. I'd guess most people who aren't doctors are in a similar boat. Labels that include the color-distinction difficulty and relative commonality would be most useful to me, e.g., "red-green (MOST COMMON — deuteranopia)", "red-green (LESS COMMON — protanopia)", and "blue-yellow (EXTREMELY RARE — tritanopia)".