Why are Butterflies Colored?
"Iridescent surfaces, such as butterfly wings, help animals to elude potential predators. When these insects fly, the upper surface of their wings continually changes from bright blue to dull brown because the angle of the light striking the wing changes. As the butterflies move their wings up and down during flight, they seem to disappear and they reappear a short distance away, looking like ethereal flashes of bright blue light. The dark undersides of their wings strengthen this effect. Combined with an undulating pattern of flight, this ability to quickly change color makes them difficult items for predators to pursue."
Causes Of Color