If the two layers never get displaced from each other very much - for example if you're not making a spandex body suit that is visible separated from the skin in a cleavage area - then use a Blender node or a bunch of them.

Make a mask, black where you want one color and white where you want the other. Use the mask to control the Blender node, and connect the two different textures you're overlaying to the two color inputs.