From some of the research I've done, the depth and magnitude of the colors has a lot to do with the exclusion of free oxygen within the pack, and during the time interval in which the contents of the crucible are dumped into the quench. This is apparently why Tony started getting more vibrant colors when he dumped the contents of his crucible faster and closer to the surface of the quench. I've read that ideally, carbon monoxide rather than carbon dioxide should predominate within the pack during heating. But I have never done this and am certainly no expert.
If the thin layer that gives us the colors really is comprised of various oxides, then reducing agents would almost certainly degrade that layer. Alternately, oxidizing agents would likely make the discoloration from the patina even worse. Surely someone somewhere has done a quantitative or spectroscopic analysis of exactly what this thin layer of surface colors is. Until I can find that, I think I'll leave the gun just as it is. I may look for some junk gun parts that still have good colors and lightly rust them, and then try to remove the staining by the electrolytic rust removal method to see if that might leave the case colors intact. I'm still interested in any other suggestions and thank all who responded so far.
