I subscribe to the genealogy site MyHeritage.com mainly for the Photo Enhancer program. It is designed to improve family photographs, but I found it can be used to enhance and colorize all sorts of old photos, including coin collection catalog plates.

As an example of an enhancement of a photograph of a person, below is an enhanced and colorized photo of an individual from the NARA Secret Service counterfeiting file.

The October 18, 1888 New York Times reported that Angilina Arsena was sentenced to "two days and $1 fine for passing counterfeit dimes."

And just for kicks I ran both the colorized Parmelee and Stickney catalog photos through the colorizing again and made some noticeable changes. I originally thought that it was a one-time process, but apparently, it can build on itself. The screenshots of the Parmelee and Stickney catalogs are from the Newman Numismatic Portal.