Can eyes change color?

My eyes r dark brown, if u look at them u cant really see the pupil...so yeah, it was raining and i was in my gradma's car looking in the mirror and i noticed that my eyes looked a kinda scarlet-brownish color and i could see the pupil, first tome i see it clearly. And it was strange, and then i checked after a few hours and they were dark brown again and u couldnt see the pupil....can someone explain???