Why are some people's eyes blue?
People with blue eyes have a single, common ancestor. A team of scientists has tracked down a genetic mutation that leads to blue eyes. The mutation affected the OCA2 gene, which is involved in the production of melanin, the pigment that gives color to our hair, eyes and skin.
The color of your eyes is a result of the amount of melanin and collagen in the outer layer of your iris, the stroma. People with no melanin and no excess collagen in their stroma look like they have blue eyes because light is scattered,a reaction similar to the reason the sky looks blue.