I am painting the base of the orrery with combination of black and silver. The idea is to give it the look of natural rock.
I also added some orange. I think this makes it look more natural, as if the rock is volcanic.
I am also experimenting with a green sheen, as if the rock comes from underwater, which would be more appropriate to go with the seaweed like material. Lovecraft describes Cthulhu sleeping in an abandoned underwater city. This would involve tiny sea creatures living on the rock that makes up the buildings, and giving them a green tinge. I like the idea that this object has been down in that city for millennia, and is discovered by an unsuspecting explorer.