Not only are 8% of men colorblind, but even compared to men who can distinguish between reds and greens, many women may live a more colorful existence. That’s because about 40% of women possess two types of so-called red cones, a key gene involved in enabling one to see the color red.
There are no men with two types of this gene, because it’s located on the X chromosome.
Men do have the X chromosome, but one only, whereas women have two, a distinction that makes for a discrepancy in how men and women see color. This gene has three times the number of variations of most other genes. Possessing a variation on this gene can inhibit one’s ability to distinguish red from green. But a variation of this gene coupled with a standard version of the gene theoretically may allow one to see more shades of reds and oranges than the average person.
The only way to get such a combination of this gene is to get your hands on two X chromosomes.
Some scientists think that the ability to distinguish subtleties in reds and oranges may have meant life or death for our hunter-gatherer ancestors. They hypothesize that since women were the primary gatherers, they needed to be able to distinguish between ripe and unripened foods, as well as between edible berries and poisonous imposters.