The field of paleontology has a sister field in the art realms. Any picture or sculpture of a dinosaur (or other prehistoric creature) that you see was created by a paleoartist. They're the ones with the creative licence to guess what colors the dinosaurs might have been, among other physical characteristics. They use modern birds and the largest animals alive today to guess at what the dinosaurs might have looked like, but don't know specifically. New observations of fossilized feathers may give them, and anyone interested in paleontology, a better clue about what ancient birds, and perhaps even the dinosaurs, looked like.
There are quite a few species of birds alive today that have iridescent feathers. Think of a raven, for instance; in some light, it looks solid black. However, if the light strikes it correctly, it has a blue sheen. This color change is caused by the difference in the angle the bird is seen from. Oil slicks also have iridescence; that's what causes the rainbow colors on it.
Some fossil feathers have odd, microscopic structures on them. When they were first noticed, around 25 years ago, paleontologists thought they were bacteria, working the decompose the feathers before and during fossilization. The paleontologists and ornithologists re-evaluating these structures on a 40 million year old fossil discovered they were actually melanosomes, a protein that scatters light. These indicate that the feathers would have been iridescent.
The fact that they've been able to document this iridenscence is awesome. Perhaps even cooler, however, is that this insight might lead to being able to determine the actual colors of ancient birds and dinosaurs, or at least the ones with feathers. It's an exciting prospect. The color of dinosaurs has been a mystery bothering paleontologists since paleontology came into being.
Credit: Science Daily- Evidence of Iridescence in 40 Million-year-old Feather Fossil