Why eyes changing colors ?

 Eye color is determined by genetics. The eyes can naturally change their color as a response to the iris expanding or contracting in the presence of light or as the iris ages. This results in the eyes gradually becoming darker or lighter in color.

The pupil can change size with certain emotions, thus changing the iris colordispersion and the eye color. You've probably heard people say your eyes change color when you're angry, and that probably is true. Your eyes canalso change color with age. They usually darken somewhat.