I don't know a thing about the original colors of the wheels, but I can tell you a tip about painting them. You DO want to mount the tires first! The "perfect" way to paint wheels in my opinion is to sand blast the wheel, etch prime the wheel, epoxy or urethane prime it (no sanding needed) then mount the tire, but DON'T bead it.
With the tire loose on the rim, cover the tire, and paint the rim. Now, unmask the tire and bead it by filling it with air. Your rims get painted with no damage from mounting the tire.
