I've answered this same question in this forum about 6 months ago. HOPPES #9 COPPER SOLVENT, not the regular solvent. I inadvertently removed some beautiful case colors from a Colt SAA about 20 years ago. I'd been shooting jacketed .45's, so I cleaned it out well and then put it aside to soak in overnight. Well, with everything that was going on back then overnight turned into 2 1/2 days. Solvent spread onto the frame and what were beautiful bright colors (new gun) were faded completely, down to bare silver metal in spots.
I'll bet if I soaked the thing in a tub of it ALL the colors would've been gone in a short time.
If you really want to get rif of the case colors I'd buy a bottle of Hoppe's #9 COPPER solvent, not the regular stuff.
