Hey jimmy50, like craigfl had said you can remove a small sample of paint from the wall and bring it into your local paint store and have it matched. There are a few things to consider before cutting a hole in the wall. Make sure if the area you are touching up is in any sort of direct sunlight it has not faded to the point where repainting the entire wall is needed. next what I do is check to see if the switch plates were painted if so pop one off and take it in, if they weren’t sometimes it’s still not a bad Idea to remove them to see if there is a large enough sample behind them to bring in for matching. Otherwise you may just have to find a inconspicuous area where you can cutout a clean quarter sized sample of paint off the wall, id go with either behind a door, or some curtains. Once you have that bring it in and have them scan it with their photo spectrometer. Good luck and hope this answers your question.