If you have a replacement barrel, I'd have it installed. It will not decrease the gun's value, that's for sure.
I'm not sure if the Colt Custom Shop will take on this job, but it won't hurt to ask. I would'nt get my hopes up about replicating the original Royal Blue finish, tho. Colt (and S&W) stopped using the blueing salts they used to use because they were too toxic by EPA standards.