The colour of the terrain must correspond in a sensible way with the height of the terrain
at any particular point (for example rocky outcrops or snow on top of mountains and
grass or soil in valleys).
Here are the levels I am thinking of:
Sand (near water).
Grass (higher than sand).
Darkish grey rocks (for mountains, higher than grass).
White snow (for mountain peaks when they're particularly high, higher than grey rocks).
From the spec:
Here are the levels I am thinking of: