Thoumont's comes with a set of blue roof textures. One obvious way to get some variety out of the set is to colorize the roof pieces. It turns out there are a LOT of pieces you'd have to do to pull this off - 6" roof, 3" roof, trusses, gables, etc. There's just a lot of pieces in the Thoumont's set.
Here are two examples of a change in color:
I admit I didn't spend a lot of time on this. I think the shading needs more black in the dark areas - I could probably play with the color ranges a little.