Wyo. Stat. § 31-5-910: Lighted lamps and illuminating devices.

Every vehicle including those listed in W.S. 31-5-901(c), except as otherwise provided in this act, upon a highway within this state at any time from one-half (1/2) hour after sunset to one-half (1/2) hour before sunrise and at any other time when, due to insufficient light or unfavorable atmospheric conditions, persons and vehicles on the highway are not clearly discernible at a distance of one thousand (1,000) feet ahead shall display lighted head and other lamps and illuminating devices as respectively required for different classes of vehicles, subject to exceptions with respect to parked vehicles. Stop lights, turn signals and other signaling devices shall be lighted as prescribed for those devices.