Bowie was born with blueish eyes. In 1962, he got into a fight with his
longtime school friend George Underwood (over George's girlfriend), and a punch
Underwood damaged Bowie's left eye. His pupil was paralyzed, becoming unable to
dilate or contract according to the ambient light.
As a result, Bowie's left eye now appears to be a different colour to his right
eye, appearing either brown or green depending on the ambient light.