Make Copper Torches More Unique

So, copper oxidizes. All copper (At least that I can think of) oxidizes, except the copper torch. And, right now, the copper torch, is kind of just a green torch. But what if copper torches got dimmer and or changed color after a while? (Which wouldn't happen with some wax, of course) That would be one way to make them more unique. (And, it's also on theme with the rest of the copper)