Case hardening on Italian guns is true color case hardening. They use cyanide salts as a carburizing agent rather than bone charcoal pack and they use a rolling quench rather than an aerated one although they are getting better at it it's still not as good as the pack method aerated quench colors. Either method the colors are fragile and is the reason they are usually protected by a coat of laquer. Vinegar will erase them in short order.