I am looking for a simple expression (I hope) to use with a flying bird animation. The bird is in profile view with 3D flapping wings. When the wing is up, it is the same color as its body, but when the wing flaps down (overlapping the body) I want it to change color. I was thinking an expression that watches for the rotation value and then tints the wing would work but I am unsure how to go about it since I have never tried any if/then expressions. Any help would be greatly appreciated. Thanks!