Colour blindness is a congenital and permanent mutation of the X chromosome, which is passed on to an offspring by the mother. The most typical case of this deficiency originates from a fault in the development of sets of retinal cones that perceive colour in light and transmit that information to the optic nerve. Men are more likely to have a form of colour blindness due to the fact that the only have a single X chromosome compared to women who have two. For a woman to become colour blind both of her X chromosomes must be mutated compared to only one for a man.
At first glance one would think that being colour blind would have no evolutionary advantages at all, however, that is not the case. US Military studies have shown that soldiers who are colour blind are much better at distinguishing camouflage compared to soldiers without the deficiency (Boring 1945). Even with this skill, most people would consider being colour blind to be a disadvantage on everyday life.
Boring, Edwin G. (ed.) Psychology for the Armed Services Washington: The National Research Council – The Infantry Journal, 1945. http://www.straightdope.com/columns/read/3037/is-colorblindness-an-evolutionary-advantage