What is a environmental variable that effect wing color

If you're referring to wing color in terms of evolution, wing color can be determined by something as small as the color of trees that particular bird is around. Those with wings that match the tree color are most likely to survive because they are more hidden from predators.

Western white butterflies vary in their wing color because it{ varies depending on when they hatch

Ithink its because more have died recently than in the past.