I'm going to guess that dinosaurs changed colors according to their environments (green in forests, brown/yellow in deserts). They evolved over millions of year

I'm going to guess that dinosaurs changed colors according to their environments (green in forests, brown/yellow in deserts). They evolved over millions of years, while skin/coat/scale color tends to change over the span of a couple millennia, at least in modern animals. So there were probably a variety of different colors even within species. Still, it would be really cool to know for sure.