Although the original colors of the fossil moths were not preserved, the researchers were able to reconstruct them because the tiny color-producing patterns in the moth scales were intact. "The level of detail preserved in the scales of the fossil moths is just spectacular", said McNamara. The fossil moths owe their color to a stack of layers inside the scales. These layers form a fossil multilayer reflector, which usually produces iridescent colour that changes depending on viewing angle. But other details of the fossil scales suppressed this effect, producing instead muted colors. "The moths basically wanted to appear the same colour from different angles – they didn't want flashy iridescence" said McNamara.Full story at Physorg.
Also, iridescence in animals may go back as far as the Cambrian era:
At different times of day and different viewing angles, the marine creatures [Wiwaxia, Canadia, and Marella] would have glowed blue, red, yellow, or green. Since the evolution of these worms coincides with the first appearance in the fossil record of animals with eyes, such as trilobites, the twinkling colors may have warned predators to avoid these armored, and perhaps unpalatable, animals.When I was a child, the color of prehistoric animals was presented as an unknowable mystery. But now, discoveries like these are commonplace-- but no less wonderful for it.