Many people with blue, green, or hazel eyes commonly notice that their eyes change color depending on:
Lighting
What they’re wearing
Makeup
Mood
This is because blue and green eyes get their color from the quality and quantity of light, not from pigment.
Thus, different lighting conditions will change the quality of the eye. Mood can change the size of the pupil, which might make the iris appear to be a different color. The quantity of melanin is not changing, but simply the way that the light is reflecting and scattering through the iris.