Hazel Eye Color Change

I was wondering what causes the "hazel" eye coloration. I understand that it has something to do with genetics, light refraction and melanin but is it anything else?
Most people that I know have eye color changes of blue-grey or green-brown and sometime blue-green. This subject is where my real question lies, my eye color changes pretty randomly from blue to grey to green to violet and rarely to brown. It doesn't change with the clothes I wear so that leaves out refraction and only sometimes will it change with my moods. Also from research i've done violet isn't a common color and is usually only associated with albinism, which I do not have.
Thanks, Meghan

[Ray T Oyakawa, MD]

All eye colors have the same pigment.  The amount determines the color.  Your eyes are probably in a different state of dilations-the more dilated the denser the pigment layer.  It also may be related to ambient light levels.

Dr. O.