Curing is time and temperature dependent, with a lesser dependence on humidity. It also varies with the binder used in that particular color (NOT just brand, color. Different colors often require a different film-forming polymer.)
A "rule of thumb" (literally) is to wait until it is tack-free. That's for a recoat. If you are masking, full cure is required—probably another 4 hours, minimum, unless you force cure.