The first portion of the section stating it is unlawful to drive impaired:
42-4-1301. Driving under the influence - driving while impaired - driving with excessive alcoholic content - definitions - penalties.And,
(1) (a) It is a misdemeanor for any person who is under the influence of alcohol or one or more drugs, or a combination of both alcohol and one or more drugs, to drive any vehicle in this state.
(b) It is a misdemeanor for any person who is impaired by alcohol or by one or more drugs, or by a combination of alcohol and one or more drugs, to drive any vehicle in this state.
(c) It is a misdemeanor for any person who is an habitual user of any controlled substance defined in section 12-22-303 (7), C.R.S., to drive any vehicle in this state.
(112) "Vehicle" means any device which is capable of moving itself, or of being moved, from place to place upon wheels or endless tracks. "Vehicle" includes any bicycle, but such term does not include any wheelchair as defined by subsection (113) of this section, or any off-highway vehicle, snowmobile, any farm tractor, or any implement of husbandry designed primarily or exclusively for use and used in agricultural operations or any device moved by muscular power or moved exclusively over stationary rails or tracks or designed to move primarily through the air.
Ergo, a bicycle is a vehicle in Colorado and it is against the law to operate it while impaired.