The standard atlas colors go from a medium blue to light blue for oceans, medium green to light green for lowland, dark orange/medium brown to white for mountains. But that just tells ya the different heights of the land not the terrain type. For that I am assuming you will want some tans for deserts, dark greens for swamps, grays for tundra, etc. I think your map is pretty cool so keep on doin' what ya do and welcome to The Guild.