Darker Extremities

A universal sensory bias is probably responsible for animals usually being colored so that their most dynamic body parts (e.g. wings, legs, arms) are darker (e.g. black, blue, purple) and the static parts (e.g. torso, breast, abdomen) are brighter (e.g. white, red, orange, yellow). See the article Dynamic Darkness and Bright Stasis in Animals: https://link.medium.com/K2vMJ6VULgb