skratch, the colors are closely related to the actual thickness of thin films of oxides and other surface compounds that will cling to the steel surface. Browning and blueing use iron oxide, red is ferrus oxide Fe2O3, and blue/black is ferric oxide Fe02 - red and black rust.
Steel can be hardened without coloring and coloring can be done without hardening. However, the bone charcoal process both hardens the surface and colors it. Case colors are very thin and do not change the hardening if worn away.
ed good was involved in some gun restorations that are/were questionable in the eyes of many on this board particurally due to torch recoloring.
DDA
