I do not know, but I could guess. Imagine that a group of engineers tries to figure out which colors they should choose for signalling. One of them proposes re

I do not know, but I could guess. Imagine that a group of engineers tries to figure out which colors they should choose for signalling. One of them proposes red and green, and the rest of team agree. All except one who says that it doesn't seem a good idea to him. When asked he couldn't bring any argumentation except "just look at it, you people, it is very difficult to see difference between red and green". This argument doesn't work because of "facts": all other people could easily see the difference. "What the heck is going on" they think, "Is he joking silly jokes or what?". They start to press him, but he is beginning to suspect something along lines "I'm not like them, there is something wrong with me, and I even do not know what. So it is better to drop this topic before they start to suspect me in taking too much of a medication or alcohol or something". It is just a guess. The only other scenario I could imagine is people with color vision deficiency were unlikely to get a position allowing them to pick colors for signalling. But the trouble with this scenario I couldn't devise a detailed story which would be looking like "real life". It is just an abstract idea.