I still have both my Fab Burgundy Hammer and Fab Blue Hammer. Both had the dull/matte finishes.
According to Bill Davis who was credited with the development of both pieces, he said the RG/differential numbers were 2.52/.020 (Burgundy) and 2.51/.020 (Blue).
When I used them back in the day (on mostly wood surfaces), I used the Burgundy on what used to call medium/holding conditions. As what's already been posted, the Burgundy Hammer had a tendency of using up its energy early. I left more 10-pins with that piece. I use the Burgundy Hammer these days mostly as a spare ball, and even then it's my third choice.
The Blue Hammer was probably more versatile, although it was used mostly on the fresh. (Some say it was arguably the best urethane ball ever made.) It had good continuation, and for my game I left fewer 10-pins with that piece. These days, I've used the Blue Hammer on certain house shots when I'm bowling pot games, as well as on sport compliant/flat patterns 40 feet or less. But I've also found it to be a much better spare ball -- I still give that edge to my Black U-dot.