From what I've seen, Colt does a pretty excellent job refinishing. I would definitely call and get a quote on pricing for the blue job and a full inspection to have it in good working order. If you think it has any collector value as it is, the reblue will pretty much kill that.
I had Colt do a reblue on my python. Didn't turn out that good. Had to send it back for different shading differences throughout. Second time around it is better but not 100%. I am hoping that the curing time will take care of it. Total fees were 280 for the reblue, 125 for the re-rolling and 40 for shipping. The once over is done for free. You can tell of the blue by looking at the inspection marks. Some get worn off.