Cut out a 2-by-2-inch section of drywall using a box cutter. Cut from a section of wall behind a piece of furniture or in an area not easily noticed. Wash the piece of drywall to ensure it is clean and free of grime.
Take the section of drywall to a paint store. Over the next few days, the staff will work with a spectrophotometer to match your paint color and sheen. This service is free at most paint stores.
Sand the surface of the drywall around the 2-by-2-inch hole. Fill the hole with joint compound using a 3-inch spreader. Allow it to dry overnight and then sand over the surface of the dried compound with sandpaper.
Paint a small section of the wall that receives a large amount of natural light. Allow it to dry overnight, and check the next day to ensure the color is a match.
Paint with a roller, so the new application and the old paint blend seamlessly. Paint also over the section of drywall that you patched.