The color of eyes is decided by the genetic endowment, which is usually formed at early age. However, when your body is not healthy, the color of eyes may change. For example, if your body lack the element of Cu, your eyes may change into green. Or if your eye get infection during swimming, your eyes may get red. So you'd better see the doctor when the eyes change the color.
Well, as a matter of fact, people's eye will not change in terms of their color. Because the color of our eyes are decided buy our genes, our DNA, which is not to be changed during our lifetime, of course, there are always exceptional cases in the world. Some people would like to change their eye color but it seems that it is impossible. However, we try to make them change color with colored contact lenses. In this way, you can change it to whatever color you care for, really convenient and easy right?