BICYCLE LIGHTS LAW REQUIRMENTS IN Ohio
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.
2011 Ohio Revised Code
Title  XLV MOTOR VEHICLES - AERONAUTICS - WATERCRAFT
Chapter 4511: TRAFFIC LAWS - OPERATION OF MOTOR VEHICLES
4511.56 Bicycle signal devices.
(A) Every bicycle or electric bicycle when in use at the times specified in section 4513.03 of the Revised Code, shall be equipped with the following:
(1) A lamp mounted on the front of either the bicycle or electric bicycle or the operator that shall emit a white light visible from a distance of at least five hundred feet to the front and three hundred feet to the sides. A generator-powered lamp that emits light only when the bicycle or electric bicycle is moving may be used to meet this requirement.
(2) A red reflector on the rear that shall be visible from all distances from one hundred feet to six hundred feet to the rear when directly in front of lawful lower beams of head lamps on a motor vehicle;
(3) A lamp emitting either flashing or steady red light visible from a distance of five hundred feet to the rear shall be used in addition to the red reflector. If the red lamp performs as a reflector in that it is visible as specified in division (A)(2) of this section, the red lamp may serve as the reflector and a separate reflector is not required.
(B) Additional lamps and reflectors may be used in addition to those required under division (A) of this section, except that red lamps and red reflectors shall not be used on the front of the bicycle or electric bicycle and white lamps and white reflectors shall not be used on the rear of the bicycle or electric bicycle.