it depends on what you want to do. you don't coat your face with a single color unless you're wanting a base. when i do zombie make up i sponge on bruises with 3 or 4 different colors and finish it off with a translucent powder so it sets better and makes the rest of the exposed skin a bit paler.
it seriously depends on what it is you're going to be. lemme know and i can help you in a bit more detail missy!