Ok, so my new place is really cute and all, but the paint color in two rooms....OMG. The bathroom is this weird orange-rust color, and one bedroom is this burgundy-ish red that gives me a headache just looking at it. So my question is, do I have to use primer or something first to paint it a lighter color? (The walls in my current place are white and therefore boring, so I've never had to deal with ugly wall colors before.)