BICYCLE LIGHTS LAW REQUIRMENTS IN Colorado
In US the bike lights die required by Law if you reading in low light conditions, The light can be attached to either the bike or to the cyclist but must be visible at least 500 feet to the front of the bicyde, so be careful how you position the light. Additional lighting must be consistent with the law specifying required lights and reflectors, so a rear light must be red.
If you ride between sunset and sunrise, both safety considerations and the law require the following:
§ 42-4-204. When lighted lamps are required
Every vehicle upon a highway within this state, between sunset and 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 feet ahead, shall display lighted lamps and illuminating devices as required by this article for different classes of vehicles, subject to exceptions with respect to parked vehicles.
Whenever requirement is declared by this article as to distance from which certain lamps and devices shall render objects visible or within which such lamps or devices shall be visible, said provisions shall apply during the times stated in subsection (1) of this section in respect to a vehicle without load when upon a straight, level, unlighted highway under normal atmospheric conditions, unless a different time or condition is expressly stated.
Whenever requirement is declared by this article as to the mounted height of lamps or devices, it shall mean from the center of such lamp or device to the level ground upon which the vehicle stands when such vehicle is without a load.
Any person who violates any provision of this section commits a class A traffic infraction.