You know someone mentioned in a forum they had dyed a flightstick of some sort with regular dye, bought at a grocery or craft store. Do a search for it, Its gotta be worth looking at. Seems a little bit of dye would take care of those pearly white buttons.
Actually, really strong trong tea in boiling water could probably tanish those buttons, but may not work as well as the dyes would.
I was thinking of dyeing a few extra buttons just to see what the results would be, can you imagiane a purple player 1 start

BTW- Don't forget to take the spring out, don't want them to rust!
Anthony