Subsequent layers of background colors will produce a rich blue/green/brown effect that will set off the warm tones in the flesh.
I am painting this figure study of hands so that I can learn the Old Master's technique of rendering flesh by building a Verdaccio (green underpainting) and then applying thin layers of flesh tones over it. Each layer builds on what is underneath. The process has been long and frustrating, but I think I'm making good progress now. I have a fantastic teacher!