The image above is an actual fossilized feather, around 40 million years old. What scientists have found in this fossil is the first evidence for iridescence, in the form of a color-producing nano-structure, in ancient feathers. There are various ways for color to appear on organic material. Some colors are due to pigment, and some are due to light refraction. The latter is what was found in the above fossil.
The simplest iridescent feather colors are produced by light scattering off the feather's surface and a smooth surface of melanin pigment granules within the feather protein. Examining feather fossils from the Messel Shale in Germany with an electron microscope, scientists have documented this smooth layer of melanin structures, called melanosomes.
"These feathers produced a black background with a metallic greenish, bluish or coppery color at certain angles—much like the colors we see in starlings and grackles today," said Richard Prum, chair of the Department of Ecology & Evolutionary Biology at Yale - ( Science Daily )
Soft-tissue fossils are among the most rare. For the past few decades scientists have noticed these tiny tubular presences on feather fossils, and until recently thought that these things were bacteria that had eaten at the feather before becoming fossilized.
Since light refracts at specific angles, creating specific "colors," they can accurately determine the color of some extinct species. Scientists hope to use this information to accurately determine the color of feathered dinosaurs.
Check out the iridescence on this bird. The bird's got some attitude too!