[watwut]

It is less, because that stat is for whites. Colorblindness is hereditary and more rare among blacks. Even among whites, some regions of the world have a lot of it (Hungaria), others less.

The other reason is that most of it is subtle colorblindness. Those people don't see black and white, they can distinguish primary colors perfectly fine. They have trouble with waaaay more subtle differences between colors - when you add a bit of green to rgb.

Yet other observation is that with exception of electricity where color codes are confusing ever for people who complete vision, the colors used in traffic, in graphs in books, in toys for boys actually tend not to use subtle shades.