"Stack map" which is a texture where the R is something, G something else, B something else, and A something else. I'm sure there is a ton of other terms for this.
Like ZacD metioned, mask out RGB, do your operations, then do an append node with R and G as the inputs with the output of that going into a second append with B.
well, the idea would be to have one mesh, with a greyscale diffuse that gets colored through the shader, the colors being R,G and B were just for simplicity
Something else to remember, which will probably make the used market eat up more, is that Walmart, Best Buy, and Toys R Us are getting into that market too.