This guide is for general information only and is not legal advice. Laws change — verify current rules with your state DOT or a licensed attorney before relying on this for any legal matter. Read full disclaimer.
The rule
Wyoming requires lamp on the front emitting a white light visible from a distance of at least 500 feet to the front. For the rear, red reflector on the rear of a type approved by the department of transportation, visible from 100 to 600 feet to the rear when directly in front of lawful upper-beam headlamps. a red rear lamp visible from 500 feet to the rear may be used in addition to the reflector. The rule applies whenever it is dark. See W.S. § 31-5-707 (Lamps and other equipment on bicycles).
The cheapest way to stay legal in Wyoming is a USB-rechargeable front white light and a rear red light or reflector that meets the spec above. A $30 light set covers it.