Surprisingly carnosaurian

surprise,
surprise:D

hope you like it?!

I wonder about how they guess the coloration of long dead dinosaurs, of whom only the bones survive as old rock.

I think the coloring is up to us :D It is a mystery :)

They don't. Almost all coloration of archosaurs is up to the artist. If they want spotting, they give it spotting, as well as stripes.

However there are a handful of dinosaurs that they have the pigmentation for and know the colors of, these are Anchiornis, Sinosaruopteryx, and Microraptor (or at least one kind of microraptor). There has also been studies that show that some hadrosaurs actually -did- have banded tails, and this was found out due to the scales' impression and how they're packed together.

Oh and recently there's been papers/studies about how some sauropterygians, and Icthyosaurs were mostly dark in coloration.

Is there a completed version of this drawing?

yes it is :) It was only a "step by step art"