Question, When you say Colt Army .45 are you speaking of a COLT brand of revovoler or are you speaking of another brand(besides Colt) that is chambered for the .45 Colt round? In answer to your question, any bluing specialist(like Jeb Stewert on these pages) can deal with the rebluing Stripping the old finish is a standard practice. That said If this is a Colt brand firearm and a Single Action Army model then it has collector value and even vigorous cleaning can devalue it. The Colt SAA in .45 Colt date back to the late 1800's..The older..the more valuable..any alteration of any sort is a BIG NO-NO...the biggest error would be to refinish the gun. FWIW, there are serial number charts that you can access to date your gun. One book to check(at your local library is The Standard Catalog of Colt Firearms by Rick Sapp and published by Gun Digest Books) So, first determine EXACTLY what you have and its value before you decide to clean it up and make it pretty. Any such act can devalue the piece by more than half. The catalog cited shows several bi-color finished versions where the frame appears to be mottled(called Color-Case Hardening) while the barrel and cylinder is almost black in color. FWIW..some of the older SAA revolvers in NIB condition will sell for 5 figures($50,000 is not unheard of) and even 3rd generation SAA's can pull in $3-4000 dollars exercise caution til you know exactly what you have..if you wish to get a pro appraisal of your specimen, go to
www.bluebookinc.com There is a fee(was $20 the last time I used it) and have the gun, amagnifying glass a small screwdriver and a tape measure at hand when you go there. Good Luck...