It's a common joke that women are able to see many more shades of colors than men do. Well, it might also be scientifically correct, at least for 50% of women. The key lies in color pigments called iodopsines. There's a iodpsine for red and green that are located in the X chromosome, and a blue one in a non-sexual chromosome. 

However, the X chromosomes can have slightly shifted green and red iodopsines, meaning a woman can carry up to 5 of them, while men only 3. These females, for example, can identify 10 different colors in a rainbow. So now you know, next time you're arguing about shades of colors, it's not that the man is trying to be obtuse. He's physically incapable of telling between the two colors.