What percentage of people are colour blind?

About 8% of men and 0.5% of women of Northern European descent have some form of colour vision deficiency; rates are lower in other populations. The common types are red-green (deuteranomaly and protanomaly). The genes sit on the X chromosome, so men need only one faulty copy while women need two.

Source: Simunovic (2010), Eye 24(5); Birch (2012), Journal of the Optical Society of America A