Fun fact: According to Wikipedia, monochromacy (being completely colorblind, can't see any color) only occurs in 0.00001% of both males and females. Red-green colorblindness, which most "colorblind" modes in games are for, occurs in 7% of the male population and 0.4% of the female population in the US.
Because of the rarity of monochromacy, games with colorblind modes tend to just change red and green to something else, usually changing green to blue (Like how Call of Duty uses green for friendlies and red for enemies in the ui, so if colorblind mode is on, it changes the friendly color to blue.).
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