How do you get paint off the wall without painting over it?

i just painted a room for my snotty sister melany (meany)lol she told me to paint it navy blue-- i did, but then she comes in and says that she wants it to be dark blue, and she doesn't want it to be painted over cuz she heard that it is easier to peal off with 2 coats, so is there anyway to get it off or is it impossible??thanksHow do you get paint off the wall without painting over it?
Blue is blue is blue. Give it a second coat of the darker blue or Navy blue or whatever. Two coats of paint will make the color more intense, and hide any residing flaws or blemishes better than one coat of paint. The first coat will act as a primer.