I've used the color swatch like that before for wireless mic identification.? It was a room where operators controlled the mic volumes from the touch panel for a big council chambers type room, and while the wireless mics were numbered, when someone had one and was holding it, in a large room it was not visible to the operators using the touch panel which wireless mic they were holding.? So we color coded the bottom (like in live sound) and then added the color swatch to the button to help identify it.? We still had the number labels on each mic and button as well, "Wireless Mic1" style label, plus a color swatch (easy "primary" colors, red, blue, yellow, green).
As Lincoln mentioned, using this by itself to ID the correct item probably falls out of ADA compliance due to colorblindness.? But having it in ADDITION to another type of label can definitely help and be a good idea.
