Scientists have been able to determine what color some dinosaurs were. I almost didn't write about this because Ed Yong did such an excellent job explaining it. But it's way too cool a result not to say anything.
In a nutshell, scientists have discovered melanosomes (color-bearing organelles) in the fossilized feathers of a number of dinosaurs. Based on the type of melanosomes found, they could reconstruct some of the colors on those dinosaurs. For example, Anchiornis huxleyi was inferred to have a russet crest.