Color blindness is usually classified as a mild disability, however
there are occasional circumstances where it can give an advantage. Some
studies conclude that color blind people are better at penetrating
certain color camouflages. Such findings may give an evolutionary reason
for the high prevalence of red–green color blindness. - Morgan,
M. J.; Adam, A.; Mollon, J. D. (June 1992). "Dichromats detect
colour-camouflaged objects that are not detected by trichromats". Proc. Biol. Sci. 248 (1323): 291–5. doi:10.1098/rspb.1992.0074.
There is also a study suggesting that people with some types of color blindness can distinguish colors that people with normal color vision are not able to distinguish. - Bosten, J.M.; Robinson, J.D.; Jordan, G.; Mollon, J.D. (2005). "Multidimensional scaling reveals a color dimension unique to ‘color-deficient’ observers". Current Biology 15 (23): R950–2. doi:10.1016/j.cub.2005.11.031.