Because we're after realism, We'll texture a real terrain from the Nasa Satellite images, we'll use images from nature, images of rocks, ground, and grass to texture this terrain.
The part of how to create terrains from Nasa Satellite images is covered in a different course. This course focuses on texturing.
I will show you where to find texture images, what kind of images you need, how to approach them, how to deal with problems in images, and how to apply them in world machine, to different part of your terrain.
No colour nodes, just pure natural images.

More info - https://skl.sh/2LxXcHF