Go to the profile of Paul Van Slembrouck
Paul Van Slembrouck
Curious about colors, brains, and emotions. || Designer of data visualization products.
I’m curious why my hazel eyes can appear anywhere from brown with gold flecks, to gray, to dark…
Jen Svogar
1

To simplify, eye color is determined by three things:

  1. amount of melanin (adds brown)
  2. amount of collagen (adds grey)
  3. amount of light in the room (adds blue)

So, say that you have brown eyes. If you are indoors, the indoor lightning can add a small amount of blue to your brown eyes to make them look grey. If you are outside or exposed to full spectrum sunlight, your eyes will generate more blue, which when added to the brown can make green or purple.