Men are also 17 times more likely to be color-blind than women. Color blindness is probably on the X chromosomes. Women have two copies, so they both have to be bad for a woman to be color-blind.
Why does this vision abnormality exist? People who are color-blind can see through camouflage more effectively. Your ancestors were probably more effective in hunting because, in a complex background, they could focus on the prey. So there was a value of being color-blind, but not anymore.