The studio should be painted white. The set, sweep set or shooting set either white, or a light grey. With grey, you can make your backgrounds anything you want, from deep dark grey, almost black (no light) to near white, or even blown out white with lots of light. You can also make your backgrounds in color by adding color gels to the light instruments used to light the background. I am coming from my experience of having my own studio for over 30 years. I would never paint a studio black. It will soak up the light and you will need much more fill to get good shots. If you are going to shoot color ever, you should NEVER paint your studio a color, just grey or white.