If you make a surface layer and add the water shader as a child, you can switch between a solid color for the water (unhook the water shader, or deactivate it temporarily, and enter a color in the surface layer) and water (activate water, no color in surface layer).
Same with the terrain: make an extra surface layer, get its input from compute terrain, give it a nice color, and hook it straight into the planet input, circumventing all other nodes temporarily.