How to Do Patch Paint on Discolored Walls

Clean your walls if you have satin, semi-gloss or glossy paint. Part of your wall discoloration may be due to residue and smudges that are removable. If you used flat or eggshell paint, don't attempt to wash it, as you can leave even more stains or worsen smudges.

Take a sample of your wall, if possible, to have an exact match mixed up at a paint store that makes custom colors. If your wall is made of drywall, choose an area near where you want to do the patch job. Score a small 1-by-2-inch rectangle with a utility knife, going about 1/8 inch deep into the wall. Pry up the corner of the drywall paper layer, and carefully peel it off for a paint sample to bring to the store with you. If your wall is not made of drywall, do not attempt this. Bring the name of the paint color you last used, or go to the store for paint chips and bring them home to compare them to your wall, choosing the one closest to the color as it is now.

Have your paint color mixed up using the same brand and the same finish. The quality of the paint and the sheen can give a color a drastically different look.

Protect your area with drop cloths. Apply a primer to the patched area to prepare it for new paint and let it dry.

Cover large areas, if doing a big patch job, with the paint until you almost reach the line of the original paint job. If the original paint job was done with a roller, use a roller; if it was done with a brush, use a brush. If doing a small patch job only a few inches square, dip a 1-inch brush into paint and tap paint on the blank area, almost up to the old paint line.

Dilute latex paint at a rate of 3 parts paint to 1 part water and mix well. If you're using oil paint because your last paint job was oil paint, do not dilute it. Dip a 2-inch or 3-inch paintbrush into the paint, and tap it onto paper towels to remove excess.

Brush the paint on the areas where the old paint just about meets the new paint using firm, quick back-and-forth strokes. Work these strokes upward and outward, into the old paint job and away from the new paint job until the brush is dry. Lighten your pressure, and brush lightly and quickly back and forth over the new paint that is covering the old paint. This will distribute and blend the new color with the old. This technique is known as feathering.

Continue adding paint over the patch and the line where the paints meet, and feather with a lighter touch as you move outward and away from the patch job in order to blend the two colors seamlessly. Stand back every now and then to give the wall a good look. Turn the lights on and off, or open and close the window, to see if the patch is more visible in different lighting situations. Keep working on it, feathering it out farther and farther, until the patch job is almost unnoticeable in any light situation.