Terraformer question

I'm wondering if its possible to hae multiple types of ground cover. I'd like to have sand under my coaster but grass around it, is this possible? If so, how do i do it?

[Dirk_Ermen]

There is a way in the terraformer that you can set a different color for specific heights of the terrain, like: Grass beween .. and .. , Sand between .. and .. .
It's possible, i'm sure. How I don't really remember.