About 2 percent of people have green eyes. Green eyes are most common in Northern, Central, and Western Europe. About 16 percent of people with green eyes are of Celtic and Germanic ancestry. The iris contains a pigment called lipochrome and only a little melanin. Genetics play a role in determining eye colour, but it’s nearly impossible to predict with 100% certainty the eye colour of a child simply by knowing the colour of his or her parents’ eyes. This is because many different genes are involved in the inheritance of eye colour, and different interactions and levels of expression of these genes can alter eye colour outcomes in children.
The structure within the eye that is responsible for eye colour is called the iris — the thin, circular structure that surrounds the pupil. In addition to controlling the size of the pupil and therefore the amount of light that enters the eye, the iris contains pigmented cells that determine eye colour. But here’s where it gets interesting: Though there are many different eye colours, there are surprisingly few types of eye pigments. In fact, nearly all eye colours are determined by how much brown-coloured pigment called melanin is contained in cells in the iris.
