Scientists from Yale University have for the first time discovered iridescent colours in fossilised feathers over 40 million years old. The feathers belong to birds that were discovered in the Messel Shale in Germany, which is famous for its detailed fossils. Using electron microscopes it was possible for the scientists to see the layer of melanin structures in the feathers responsible for colour, and known as melanosomes. This could mean that soon the colour of feathered dinosaurs and ancient birds would be known.

Nanostructures, which for many years were thought to be bacteria, are now known to be the melanosomes responsible for producing the vivid iridescent colours. The iridescent quality of the colours is produced by the angle of observation. Scientists have noticed a smooth layer of melanin structures in the Messal Shale fossil feathers. The birds to which they belonged would have had an overall black colour with greenish, bluish or coppery colours depending on the angle, much like starlings.

It is thought that small fleet-footed feathered dinosaurs may have been quite brightly coloured plumage. It would seem that as long as sufficiently well-preserved fossils of feathered dinosaurs exist it may be possible to study the melanin structures in the feathers and determine their colour.