I am using colored file labels, cut very thin. I got the suggestion from a grandmother who was visiting the class. Her husband was a doctor and was retiring, so she had tons of chart labels. By the time the kids get to the black belt, they have a very colorful recorder. You probably wouldn't want to do this on a really expensive recorder, though, because they don't come off very well. However, ours are "cheapies" so it doesn't really matter.