Eyes definitely can change color. Some change permanently over time, like my grandma had green eyes then they turned grey. Some change every day, like mine. My eyes used to be blue, now they are colorful, blue/grey/green and I have amber spots in my eyes. My eyes change alot. Somedays its solid green, other its blue, or blue grey. When I cry, they turn more blue, and I've had friends tell me that when I tend to get angry or fired up, they turn very green, and so I have a couple guy friends that'll say "uh-oh..her eyes turned green, be careful!!" after they've done something to irritate me xD
That being said, some peoples eyes do change just because of light. If I am outside on a sunny day, or have a light shined in my eye, they will appear to be a light, solid green.