The iris is the coloured part of the eye : this is what gives eyes their colour. It is determined by a pigment called melanin. If the melanin is highly concentrated, the eyes will be dark (brown, black or hazel) while a lighter concentration will give light eyes (blue, grey or green).

All babies have a common point: they are born with navy blue eyes, whatever the colour of their skin. The ultimate colour of the eyes is set between 3 and 12 months old. It is dependent on the parents :
- If both parents are light-eyed, the child will be light-eyed.
- If both parents are dark-eyed, the child will be dark-eyed… Except if the parents are carrying a « light eye » gene bequeathed by one of their ancestors.
- If one of the parent is dark-eyed and the other is light-eyed, the child will have as many chances to be dark-eyed as to be light-eyed.