John,
It depends on conditions. Lately the water has been off-colored, so chartreuse has worked best. I was using a 3/0 Zonker type fly with a rattle encased in mylar tubing. When the water clears, I use EP Baitfish flies, Deceivers, Clouser Minnows, and Mighty Minnows in gray/white, olive/white, chartreuse/white or blue/white, usually 2/0-4/0.
Steve