Not that much happens in the eyes, with regard to emotion: "The iris is a muscle that expands and contracts to control pupil size. The pupil enlarges in dimmer lighting and grows smaller in brighter lighting. The pupil also shrinks when you focus on near objects, such as a book you are reading. When the pupil size changes, the pigments in the iris compress or spread apart, changing the eye color a bit.
Certain emotions can change both the pupil size and the iris color. That's why some people say their eyes change colors when they're angry or loving."
(Excerpt from here: http://www.allaboutvision.com/conditions/eye-color.htm)