The 3rd and best method of achieving gold colour requires highly specialised industrial equipment but costs about $4000 per run and can only accommodate 20 frames. It's a permanent molecular bond that will never come off by normal means... unless you deliberately scratch it with diamonds
Or u could just make molds of each piece then cast them in solid 14 or 18k gold. That would probably be the most expensive and ineffective way, but guaranteed the gold won't flake or scratch off. Lol