What does blue mean on a gun?

Answer:

Blueing is a chemical finish applied to a firearm to prevent rust.
The color can actually be anywhere from black to brown as well as blue.
The amount of blue worn off a used or antique firearm affects it's value.

First answer by Marcucco. Last edit by Marcucco. Contributor trust: 90 [recommend contributor recommended]. Question popularity: 6 [recommend question].