Low-poly style layered textures. need help!

Hi My name is joe, and my current problem is that I can figure out a way to layer simple colors on a landscape to create a low-poly style. I have been trying for a while now and I just cant seem to find out how. any help would be appreciated.
633bfe7f0b2d764ddd856ee5c1db59e4efd20d8b.jpeg
something like this.