It may be a similar story for eye colour, he suggests, with greater quantities of pigment building up in the months or years after birth. "The main pigment in the eyes is melanin and it"s the way that melanin is distributed that gives you the different eye colours," he says. "Simply classifying them: you"ve got blue eyes, some people also talk about grey but really it"s a variant of the blue, then you"ve got the hazel and green combinations, and then you"ve got the brown, and that can be slightly brown or extremely brown. All of that"s related to how much melanin is there."