Did basically the same thing as you, but yours is alot neater.
I used pieces of string - one loop on hose #1, two loops on #2, etc.
I did this after hooking my front mount snowblower back up this year - the lines on the blower were not color coded and I probably spent a half hour getting them hooked up to the proper connections.
Was going to try refreshing the painted color dabs that were on them when the tractor was new, but figured that would just wear off again. Was also going to try sticking something on, but, like you state, knew that wouldn't last too long.
I like those color coded end caps; would be a nice clean solution.