Why do I see two different colours in each eye?

Heterochromia. The appearance of the iris (color) of the eye to have two different colors often shows up early in life. Heterochromia ("different color") is usually normal. If this appearance develops in adulthood, it should be evaluated by an eye doctor. If one eye appears "bluer" than the other, the issue may be on the cornea (clear window of the eye).
Almost always normal. Many people have flecks of darker color in the iris (colored part) of the eye. If the colored area are changing, or if one eye color changes and the other one doesn't, you need an eye exam with an ophthalmologist. Some medications for glaucoma and also to darken and increase lashes can cause a darkening of color in some people.