My wife wanted to paint the inside of my brown, brown and more brown truck camper. I was against the idea because I thought it would look terrible and scratch everywhere.
Well, the truck and the machinery is all my department and the interior is hers so I went along with it and WHAT A HUGE IMPROVEMENT!!! Should have done it years ago!
She used to be a painting contractor and knew what she was doing, did pretty much what the guys here are saying: scrub first, use quality primer and paint. It's been a few years now and still looks great. We both like teals and blues and now that's what we have.
I suppose resale would take a hit on a newer rig. I'd be hesitant to buy a painted rig because I'd think it was hiding something (other than all the ugly brown) but my camper is an '87. It's got no resale anyway.