Winter fishing on the Gunnison will mean nymph rigs and the occasional streamer twitched slow. An attractor nymph followed by a smaller midge or baetis is your best bet.
There may be some decent midge hatches.
Patterns/Bugs:
Nymphs: Prince nymphs 14-18, Pats Rubberlegs 8-12 or Jigged Pats 8-12, Black and Blue Copper Johns 14-18, Pheasant tails 18-22, Juju Baetis 18-20, Disco Midge 18-20, Rainbow Warrior 18-22, Flash Midge Pupa 18-22.
Dries: Griffith Gnat 18-22, Sproat Midge 20-22, Parachute Adams 18-24
Streamers: Sculpinator, El Sculpito, Dungeons, Galloups Barely Legal, Galloups Butt Sump.