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Some babies are often born with blue eyes that get darker over time. Why does this happen? It’s because of melanin. Melanin, produced by cells, is the pigment that’s responsible for giving you the color of your skin and hair. Just as sunlight turns the skin a darker shade, it does the same thing in the iris. When a baby enters the world, melanin production starts in the iris, which can lead to eye color changes. Just a smidgen of melanin and a baby will have blue eyes; add some more and you get green, gray, or hazel; even more and a baby’s eyes will be brown or even black. (Source)