The Ruger Vaquero SA revolvers and a few other use a dye to simulate color case hardening, I have been told that to long an exposure to some solvents can degrade or remove these dyes. I have three Vaqueros and have never had a problem. I use Hoppes, ML 10, and a few other comercial cleaners and solvents, including Butche's Bore shine. A few years back I also heard that Hoppes #9 would or could cause nickle finished, firearms to start flakeing, I do noit own any nickle finished firearms so I have never tested that rumor either. The internet is full of assinine rumor some has a slight basis in fact, some is totally made up for what ever reason.
FWIW Just don't soak, or leave the solvent on tha Case hardened part for a long time. wipe on, wipe off, oil. /ubbthreads/images/graemlins/grinning-smiley-003.gif