While there are no laws in Arkansas that specifically restrict underglow, it's only legal to use it while driving on private property. Neon aftermarket lights are unlawful while the vehicle is being driven on a public street. Green, red or blue lights are against the law in Arkansas.
Federal Motor Vehicle Safety Standards govern the location, color, quantity and purpose of all lamps and reflective devices on motor vehicles. According to the Transportation Department, lights enhance the conspicuity of motor vehicles on the public roads so that their presence is perceived and their signals understood, both in daylight and in darkness or other conditions of reduced visibility. For instance, everyone knows that white is headlights. State regulations govern the use of after-market light kits in Arkansas.
Neon Lights are Banned
Using neon or any other exterior lighting not installed as original equipment by the vehicle manufacturer prior to a retail sale is unlawful while the vehicle is being driven on a highway or public street. You can use one courtesy lamp for running boards on each side of the vehicle. It must be a white light without glare. You can have the lights illuminated for a show or other event while you're parked. However, if the vehicle is being moved or driven, the lights must be turned off.
White Lights for License Plates
The license plate must be illuminated with white light, which makes it both visible and legible for at least 50 feet from the vehicle. The light must not be so strong as to make the plate illegible. No colored lights may be used. License plates must be illuminated whenever headlights are necessary.
No Colored Lights on the Vehicle Front
The use of green, red or blue lights on the front center of your vehicle while you are driving is against the law in Arkansas. Red, blue, amber, flashing and/or rotating lights are permitted only on authorized emergency vehicles or a school bus. For regular vehicles, flashing lights can be used to indicate a turn, on the berm of the road to signify an emergency or to warn other vehicles to use care in approaching, overtaking, or passing.
If you have an extra light on your vehicle that is more than 300 candlepower in intensity, you must direct it so that it strikes the road no farther than 75 feet from your vehicle. This clause does not refer to headlights, auxiliary or spot lamps, flashing turn signals, school bus warnings or emergency vehicle warning lamps. No more than two ornamental light-emitting diodes (LEDs) with white lights may be mounted on the front of a vehicle.
Lay off the Neon at the Vehicle Rear
Lay off the neon and stick with factory furnished lighting, unless you are operating a "street rod" or custom vehicle. If you have either kind of vehicle, you can use use blue dot tail lights for stop lamps, rear turning indicator lamps, rear hazard lamps, and rear reflectors.
Penalties for Light Violations
If your vehicle violates the emergency vehicle regulations, you can be charged with a Class A misdemeanor with fines up to $2,500 and up to one year's jail time. Violation of any other clause related to lights is a lesser misdemeanor with fines of up to $500 per offense and court costs.