Surface prep is key with the cold blue. Degrease *very* well, apply multiple coats, and oil it well.
I used Oxpho-Blue on the top of a Colt 1911 from 1953 where I had to plug holes from an aftermarket sight rail. The color matched well and it’s has stood up to lots of range time. Can’t really say how it wears since I don’t carry the gun but it hasn’t rubbed off from simple handling.