yes, mine change all the time, depending on what I'm wearing, what the weather's like (more sunlight reflects them back brighter, and shows more blue), what my haircolor is, and my mood.
However, like it was stated before, they never *really* change color, it is only that the colors in your eyes are enhanced by the colors that frame you, and the dialation of your eyes.
When you are, for example, feeling an emotion very strongly, your eye muscles contract, and more color can be seen. I'm often told that the amber splashes in my eyes are more predominant when I'm upset, but then, more of the colored part of my eyes are seen at this time, and my skin gets very floushed, which brings out the gold.
Also, your syes will change colors slightly when you have different nutritive balances. The rims of your colored parts get darker when you have folic acid deficiencies, and you will have less color to your eyes when dehydrated.
By contrast, when sick because the eyes are excreting much more tears, and also when crying, the color of your eyes will be enhanced by the amount of fluid over the cornea, giving your eyes a deeper, richer hue. This is another of the many reasons why actors and actresses make a point of drinking lots of water.