Hi, Gary,
Flame bluing or fire bluing provides a result that is pretty, but not very durable. Worse, it can hurt the heat treatment of parts that need to be hard and create problems, like softening the locking lug area of a slide. Except for small, non hardened parts, I don't recommend it.
In some guns, of course, a factory flame blue color is part of the heat treatment and is carefully controlled.
Jim