@TheBadger: it's not hard at all. Just copy (ctrl+D) the planet, disable the rendering of atmosphere (you only need one), and hook a new line of nodes into it's input. If you use the same main terrain, but change one of the lines (add some major displacement), and have some different colors in surface layers, you'll see the difference right away. Just two terrains 'alternating in appearance'.
If you use exactly the same terrain but add some minor displacement (and different colors) at the end of the line of nodes (surface shaders), and blend these by a distance shader, you'll have some subtle difference right in front of you, but not in the distance. Something like that.