Make sure you get the right sheen also. Flat, Eggshell,Satin or S/G. Take a sample of the color about the size of a quarter and have it matched at the paint store or Lowes. Best bet to paint the wall from corner to corner. If not. Take some out of the can and thin it with a little water. Most times you see the touch up because the touch up is a thicker coat then the older sounding area. Also if the surrounding area was rolled and not brushed use a mini roller, you will get a similar finish.