Board Thread:Fan-made Monsters/@comment-27950421-20161031211814/@comment-27950421-20200512153724

Well just about any stone is feasible. Hell, if you're bored and just want to practice coloring, you could spend some time popping out different palette swaps for different types of rock.

But yes, sandstone, shale, limestone, all of those would be a prime rock color to use.