There's not really much info on definitions for OC and CC as far as Colorado law is concerned. There's no "printing" rules as in TX, and no holster specs for CC or OC. Concealed in CO implies full coverage with no exposure of any component of the sidearm. OC would be carrying in a manner that there would be no mistake that a sidearm is being carried. Go figure. I'm just happy there's a big gray area for interpretation. It allows those of us with CO CCW's to carry as we wish, as long as we abide by the basic rules (gov't buildings, schools, airports, Denver, etc).
Oh and as far as holsters? Buy and try, I have holsters that I thought I would like, but ended up going with something else.
Right now I carry a 1911 in a Blackhawk CQC Serpa. But sometimes I'll change over to a leather shoulder rig. Just depends on my mood, destination, climate, comfort level, whatever.