To make a change, let your fabric be your guide. In fact, this is a good approach to take even if you're starting from scratch. Fabric, carpeting, and tile are available in a more limited range of colors than is paint, so choose them first and then decide on your paint color.
Any fabric can suggest at least three options for wall colors, each of which will produce a different feeling in the room. Once you identify the options your fabric offers, decide which one creates the mood you want to evoke -- cozy, calm, relaxed, energetic, playful?
Of course, starting with the fabric works for any room in the house, not just a room with a sofa. Bedding and draperies provide easy starting points for adding color to bedrooms and adjoining baths, and even in a powder room, the window treatment can suggest an exciting wall color.