Also don't underestimate the effect of surrounding colors and light on eyes. My eyes appear to change color depending on mood and surrounding, ranging from light gray through blue to dark green. Since I can't see my own eyes anyway, I never paid much attention to it, but my sister apparently uses it to discern my mood. Apparently, my eyes only turn dark green when I'm enthusiastic or very angry.

I don't have many pictures of myself, but when I checked my old school photos, I did notice that I always had the same color eyes as the background, but then again, those backdrops were usually grey, blue or green. Never tried purple though.