You should probably contact Colt first.
Since they made these SAA's they could blue a cylinder to match.
I think they still offer SAA finishing and that's were I'd start.............

Contact - Colt's Manufacturing LLC

Contact Colt’s Manufacturing Company LLCPhone: +1 800-962-2658Plus 1 8 0 0 9 6 2 2 6 5 8Fax: +1 860-244-1442Plus 1 8 6 0 2 4 4 1 4 4 2Do Not Send Firearms Without An RMA. Serial Number Lookup Instantly retrieve vital product details, warranty information, and exclusive insights…

www.colt.com

Other options for top quality bluing........NOT some local gunsmith who may still do a little bluing, and almost always does it poorly.
Some of these are restoration services able to replicate old types of gun bluing.

Glenrock Blue--Custom Gun Bluing
Among the very best, possible THE best.

Doug Turnbull Antique Firearm Restoration
The best of all firearms restoration services.........prices are high, but so's the quality.

Ron’s Gun Shop. Antique Gun Restoration, Gun Bluing and Custom Gun Blueing Services
Another top restoration service.

Precision Bluing | America's #1 Bluing Company!

Ten Ring Precision | Custom Guns Based in San Antonio

Old South Restoration| Firearm Restoration Dyersburg TN

OSR Firearm Restoration, Specialize in period firearm restoration. Color Case Hardening, Charcoal Blue, Rust Blue, and Hot Blue.

www.oldsouthrestoration.com

 

If Colt is still taking work in, that's the way to go. If not, Turnbull is one of the best at replicating original finishes. Precision Bluing is a nice group to work with, but they washed out some screw holes on the last rifle they did for me. Good for the average Joe, but not really acceptable on a higher end gun.

 

I took a 3rd gen cylinder to Lever Action Bill (1-307-431-9194) to match the rest of the gun and he did the work perfectly very very happy check him out

 

I's likely a hot salts dip- the degree of polish determines the luster.

 

Baron Technology can polish and produce a Royal Blue without issue. I had them do my old Combat Commander. It looks like my older Python. They can recut any trademark or roll marks with in-house engravers if the polishing required affects them. I believe they do work for S&W and Ruger.