Although some people have blue eyes, and many babies are born with particularly deep blue irises, no one actually has blue pigment in their irises. They're just a trick of the light.
With the news of Elizabeth Taylor's death, many people's thoughts have turned to eye color. It's known that her famous violet eyes were mostly the result of make-up and photo coloration, but even outside of the world of starlets many people rhapsodize about blue eyes. This is especially true with parents, who are startled by the deep blue of their babies' eyes. When people say that their children's eyes are sky blue, they're telling the truth. Blue eyes are blue for the same reason the sky is blue - scattered light.
Irises are made up of three layers, a thin top and back layer, with a spongy layer in between called the stroma. Any layer can have pigmentation in it. There are a few different colors of pigment that come into play. Most people have either dark brown or yellow pigment in at least one of these layers. The combination of yellow and brown go into making brown and amber-colored eyes. Brown-eyed people have these pigments in each layer of the iris, giving the eye a strong brown color.
Even if the overall color of the eye doesn't change, babies and young children tend to have more intensely blue eyes than adults. As people age, the particles in the stroma get bigger, and scatter white light. Add a layer of white to the blue, it comes to look more grey. People can see this kind of pigmentation in weather. A dry sky is made up of tiny particles that scatter blue light and make the sky look blue. As clouds start to form water molecules fill the air, and the color of the sky changes to a whitish grey.
Original Source http://io9.com/hows-that-no-one-really-has-blue-eyes