Some modern guns made of alloy steels have been chemically colored, "From the Factory". Note that this is just colored, Not Color Case Hardened. Part is heated to around 200F & the chemicals painted/daubed on. This can be done with Cold Blue.
Note also this is not the same process as "Torch Coloring" where the torch is held on one spot long enough to produce the color desired & Also Destroy the previous hardening. The Chemical coloring does not affect the integrity of the metal but of course will never look as well as a bone charcoal job, though can look as well as a lot of cyanide ones. I have no idea how well it holds up, but at least is easy to do again.
