These Images show, what I meant with hue-shift. But do color blind people actually see red and green as yellow? Such that they also are incapable of discriminating between red an yellow (and green and yellow)?
This is a common misconception by people who see images processed by color blindness simulators, so I’m going to answer: I have a slight red/green “blindness”, and I do
not see red or green as yellow. Most of the time when I get a color “wrong”, I just see it as a grayish red when it’s supposed to be green, or as a grayish green when it’s supposed to be red. Often it even switches forth and back (sort of like when you see an optical illusion, and you can’t decide whether the object you’re seeing is concave or convex. I hope that gives you an idea.). So, while (at least to me) it mostly happens with colors of low saturation (which means that they appear shifted towards gray/brown), it really doesn’t look like yellow, or brown, or gray or anything, it’s just “ambiguous” with a slight tendency to either red or green and a brownish/grayish tinge (again, because the affected colors have a low saturation). Interestingly, my knowledge about the object also affects how I see it – like, if the color of an object is ambiguous to me, and some one tells me that it’s green, I will actually start to see it as green and think “how could I not see that before?”. It’s quite funny.
As you can imagine, I have found no simulation that accurately represents what I see, and I think it’s impossible to simulate. However, there is of course a problem in judging this – since I see colors differently, I probably see the simulation differently as well, therefore it might be possible that people with “normal” perception perceive the colors in the simulation as I would perceive them without the filter – though I doubt it (this essentially leads to the problem mentioned in BUG’s post). Anyway, I think that these simulations are only supposed to give you an idea of how big the
contrast between two colors is,
not exactly recreate what a color blind person sees.
But as has been said before, please keep in mind that there are varying degrees of color blindness. Some people can’t distinguish red and green at all, others are only unable to distinguish specific combinations of hues, brightnesses and saturations, and the ranges are different for every person. There are also some people who can’t distinguish blue and yellow or can’t see any colors at all, although that’s very rare.