Wyo. Stat. § 31-5-919
Whenever the load upon any vehicle extends to the rear four (4) feet or more beyond the bed or body of the vehicle there shall be displayed at the extreme rear end of the load, at the times specified in W.S. 31-5-910, two (2) red lamps, two (2) red reflectors located so as to indicate maximum width, and on each side one (1) red lamp located so as to indicate maximum overhang. There shall be displayed at all other times on any vehicle having a load which extends beyond its sides or more than four (4) feet beyond its rear, red or fluorescent orange flags, not less than twelve (12) inches square, marking the extremities of the load, at each point where a lamp would otherwise be required by this section. Lamps and reflectors required in this section shall comply with the regulations of the superintendent.
W.S. 31-5-919