[QUOTE=Sarah Woodruff]
I thought that the number or size of melanin cells would determine how much “brown” pigment there would be in the iris, like with skin colour.
[QUOTE]
that may in fact be the case; I really don’t know enough about pigmentation to say. I know melanin production does affect eye color, so some genes involved in it eye pigmentation surely affect at least melanocyte manufacture and/or competence in melanin production, if not also size (I don’t know whether or not that’s a factor). melanin’s just one of many different factors in coloration of the eye, though; it’s the interaction of all these factors that ultimately produce the color you see.