I accidentally discovered how to remove bluing when I attempted to clean my Ruger Old Army cylinder the first time by dropping the cylinder into a pan of boiling water that had some vinegar in it. Left it in too long. Big mistake. I was heartbroken. The cylinder looked like it was 100 years old. Down to the original white steel, for the most part.
Upside: I learned how to use Birchwood Casey Cold Bluing solution. All better now.