There is no doubt that eye colour is due to genetics, inherited from the parents of a child, however it is also well known that most babies are born with blue eyes. Why?
Ultimately, it is because the melanin within they eyes of a baby has not been fully deposited in their irises or fully developed yet. Melanin is the protein, a brown pigment, responsible for the colouring of your hair, eyes and skin. It darkens due to exposure to ultraviolet light. The amount of melaninthat a baby will develop is coded for in their genes, resulting in different eye colours due to different amounts of melanin being coded for. A high concentration of melanin in your irises result in eyes appearing brown/black, less melanin produces green/grey/light brown eyes, and irises containing very small amounts of melanin appear blue/light grey.
How does eye colour develop?
The production of melanin usually increases during the first year of a babies life, resulting in a deepening of eye colour. The time taken to reach a stable colour varies from around six months to two years, and is affected by several factors, many of which environmental. This means that some people have eyes of two colours, and some people experience a change in their eye colour throughout their lives.
But, not all babies?
The likelihood of an African, Asian or Hispanic baby being born with brown eyes is common, and blue eyes less so. Why? Darker skinned individuals tend to have more melanin in their eyes, resulting in a darker colour. Although, this may still change or deepen over time.