It’s the same stuff that makes us suntan-a pigment in our skin and eye balls called melanin. The amount of melanin just keeps getting bigger. The more melanin, the darker our hair, eyes and skin are. If there is only a tiny amount in the colourful parts of our eyes, our eyes look blue, whereas a lot makes our irises brown. We keep changing eye colour until we’re two years old!
When you’re born, you have very little melanin in your body. Melanin is the natural pigment of the body and, as you get older, your body produces more of it. If there’s very little there (like in babies), your eyes are blue. As more is put in, you get blue-green, green and brown eyes.