It's not permanent, and I have to replace it frequently, but I use different color electrical tape and or fingernail polish to mark my different size sockets and wrenches. I only do this to the frequently used sizes when I work on my motorcycle. 8mm is black, 10mm is red, 13mm is white, and 17mm is brown.
I don't know what colors I would use working on my Jeep because of SAE and metric, or the odd 15, 16, 18mm sizes,