Its the type of answer that pops up on guitar building forums quite often
the short answer is no, it isnt possible.
maybe something is possible - but its going to need a lot of research to get it right and will probably still rub off easily if its a coating
apparently you can dye aluminium with lots of chemicals but getting a hard enough alloy would be difficult and it would still wear off as soon as you levelled them
Cf frets is a possibility.. again lots of research would be needed. I have heard of delrin rod being used instead with quite good results.. pretty permanant change though because it would need to be installed a completely different way
gold is available