Why do my eyes constantly change color? they are usually grey, but have changed to brown, hazel, blue, and green. is this normal?

Light pigment: Lightly pigmented iris' can take on different hues under different lighting intensities. It is normal.

Appearance: Some fortunate people have multicolored eyes. In the microscope, there are several colors on the iris: blue, brown, green and so forth. When you wear clothes that match one of the colors, the eyes appear to change.