Up until about 1920, Colt commercial handguns had what they called their "trade finish," that today is sometimes called "charcoal blue." This was a deep, highly polished black-blue finish. They also had was was called the "militiary finish," which was applied by the same method but with less polishing. This made the color more blue and the polish flatter. Commercial New Service and U.S. Model 1909 revolvers had the high polish finish. Model 1917's were for the most part were "military finished."
After the war during 1919 or 1920, (give or take) Colt discontinued the charcoal process and went to an entirely different system, that they called "gas oven blue,"which resulted in a very blue-blue color over what appeared to be a wire brushed surface. This was used on both commercial and military handguns up until 1939 when the factory was retooled and a Parkerizing facility replaced the gas ovens.
So the blued finish on a New Service revolver depends on what it was, and when it was made.
Other revolvers made on the New Service platform inclued:
The New Service Target
The Shooting Master.
The FitzGerald Special
U.S. Models 1909 and 1917