The glow bird is a bird concept I had trying to think of birds that would live in huge underground cave systems.

By default, the glowbird is a cool bluish purple to replicate the various colors of crystals found in the underground cave systems. It has a dark hue to most of it's feathers to camouflage within the darkness.
When it's mating season, it flashes the limited palette of cool colors it has into a warm amorous pink. The female chooses the male based on his mating dance and how he coordinates his movements according to the pink glowing feathers he has.
When threatened, the glow bird extends his wings and flashes all the colors he can muster around his body to scare off predators with a warning flashing glow.

But don't be fooled, around the world in various cave systems, there can be a multitude of colors the glow bird can glow.