The following very interesting article ...

The following very interesting article states that 12% of all woman actually have four cone types in their eyes. But because in most cases the sensitivity to color of the fourth cone is not(!) very different from the red and green cone their brain cannot see more colors than people with just three cones. However in their study with seven woman, which have four cones, one of the woman actually could see more colors than usual. If that is representative it means that 12/7 = 1.7%(!) of all woman actually can distinguish more colors than the average person with only three cones in their retina.

I wish you a colorful christmas!

http://theneurosphere.com/2015/12/17/the-mystery-of-tetrachromacy-if-12-of-women-have-four-cone-types-in-their-eyes-why-do-so-few-of-them-actually-see-more-colours/