This is pretty neat: scientists are able to interpret the color patterns of 100-million-year-old fossil feathers .. by microscopic analysis of melanosomes that somehow survived the fossilization process:
Microscopic analysis of the dark bands showed they displayed a distinctive granular texture, made from thousands of tiny, densely-packed flattened spheres.
Researchers had previously interpreted these as fossilised bacteria, preserved as the feathers decomposed. But analysis of modern birds' feathers showed a similar structure. "There are particular cells that cluster into the dark areas of modern birds called melanosomes," explained Professor Benton. [...]
The Yale team believe it could identify brown, red, buff and even iridescent colours. The technique may be applied to other creatures to reveal the colour of fur or even eyes, the team believes.