What subtle coloration is often visible on the underside and wing lining, particularly during display?

Answer

A distinct, subtle pinkish or salmon hue

A distinct, subtle pinkish or salmon hue is often visible on the underside and the lining of the wing, especially when the bird is in flight or displaying.

What subtle coloration is often visible on the underside and wing lining, particularly during display?
raritybirdanimalFlycatcher