The amount of melanin in our iris will determine which kind of eye color we will have. But at the beginning, I think the eye color is determined by the gene that a baby inherits from his or her parents. Sometimes the expression of the gene will account for eye color. And if there are any small changes in the gene, the color of the eye will changes. if a dominant gene transformed into a recessive gene, or a recessive gene turned into a dominant gene, the color of the eye will changes. I know this is rare case but it happens in our daily life. When your baby sees the light, the light will kick-starts melanin production in the iris, the color of the baby's eyes will change. I heard that the color of the eyes can change from blue to green then to gray or hazel and to black with the increase of melanin. Just as sunlight can turns our skin into a darker shade.
