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Jul 07 2017, 12:02
I am sitting in the 6th European Set Theory Conference in Budapest, and watching all these wonderful talks, and many of them use colors for emphasis of some things. But yesterday one of the talks was using "too many colors", enough to make me make a comment at the end of the talk after all the questions were answered. Since I received some positive feedback from other people here, I decided to write about it on my blog, if only to raise some awareness of the topic.
There is a nontrivial percentage of the population which have some sort of color vision deficiency. Myself included. Statistically, I believe, if you have 20 male participants, then one of them is likely to have some sort of color vision issues. Add this to the fairly imperfect color fidelity of most projectors, and you get something that can be problematic.
Now, I'm not saying "don't use any colors". Not at all. Just keep in mind that some people might have problems with your choice of colors. Using too many colors can be distracting, and one of the slides in the said talk had black text almost on par with the rest of the colored text. This is far from ideal. But since color deficiency can vary from one to another, let me only give an account of my own personal experience. I cannot do anything more, after all.
I have a mild red-green issue. But this means also that yellow and bright green, or light orange, all mix together sometimes; and darker greens can be red or brown (which themselves are often mixed); and blues can mix with purple, and sometimes with pink as well. One other effect of color deficiency is that you are more sensitive to brightness and darkness (the eye compensates the damaged cones by having better rods, so your night vision gets somewhat better, for example).
So when you have a slide with some pink/purple and green/yellow/orange and some blue and some red and some black, my brain will not read the text. My brain will try to make sense of the colors. Not to mention the terrible eye strain coming from the brighter colors (here the quality of the viewing media is important, I'm sure that I'd be fine watching the same slides on a proper computer monitor). There were slides that I had to turn my eyes away from the talk. Yes, it was pretty bad.
What can you do about it? Don't use colors when you don't have to. Use boldface or italics for emphasis when possible, or different font family entirely. If you want to use colors, using them sparingly, and try to avoid relatively close colors together and certainly try to avoid brighter colors like light green or yellow. If you know a color blinded person, you can maybe ask them to give some critique on your choice of colors.
Some people commented to me after my remark that they prefer the colors, and they are helpful. I understand that. Again, the point is not to get people to use colors. Just... to use them intelligently. Colors are like spices. I'm not trying to get you to cook without spices, but you're not going to serve a dish entirely made of cinnamon and cumin.
In the name of all color vision deficient people, thanks in advance for your consideration!