California neon underglow laws are found in California Vehicle Code, Division 12 – Equipment of Vehicles, Chapter 2: Lighting Equipment.

Is neon underglow legal in California?

California law allows additional aftermarket vehicle lighting which includes neon underglow. In California neon underglow is legal, as long as you follow these restrictions:

• Red color may not be visible from the front of the car
• No flashing lights are permitted
• Underglow must not emit more than 0.05 candela per square inch
• All aftermarket lights must not be installed within 12 inches of vehicle’s required lights

We also highly recommend avoiding blue, red and green colors on any aftermarket lights including underbody glow, as these colors are typically used on emergency vehicles.

In case your underglow system emits more than the allowed 0.05 candela/square inch, permitted colors are white and amber in the front, and red in the rear of your vehicle. Review your street glow lights package carefully, and if possible have the original packaging in your car as additional proof if required.

California vehicle lighting laws

Below are all relevant excerpts from California Vehicle Code (Div. 12, Chapter 2: Lighting Equipment) that limit, restrict or permit certain aftermarket lights to be installed on vehicles.

Article 7: Flashing and Colored Lights

Flashing lights are prohibited on vehicles except as otherwise permitted. […]

Besides turn signal lamps, exceptions for flashing lights include emergency and other vehicles as described in Article 7.

Article 10: Diffused Lights

(a) Any vehicle may be equipped with a lamp or device on the exterior of the vehicle that emits a diffused nonglaring light of not more than 0.05 candela per square inch of area.

(b) Any diffused nonglaring light shall not display red to the front, but may display other colors. A diffused nonglaring light shall not resemble nor be installed within 12 inches or in such position as to interfere with the visibility or effectiveness of any required lamp, reflector, or other device upon the vehicle. […]

No diffused nonglaring light on a vehicle shall resemble any official traffic control device.

Article 15: Light Restrictions and Mounting

This section applies to the color of lamps and to any reflector exhibiting or reflecting perceptible light of 0.05 candela or more per foot-candle of incident illumination. Unless provided otherwise, the color of lamps and reflectors upon a vehicle shall be as follows:

(a) The emitted light from all lamps and the reflected light from all reflectors, visible from in front of a vehicle, shall be white or yellow. […]

(b) The emitted light from all lamps and the reflected light from all reflectors, visible from the rear of a vehicle, shall be red […]

(c) All lamps and reflectors visible from the front, sides, or rear of a vehicle, except headlamps, may have any unlighted color, provided the emitted light from all lamps or reflected light from all reflectors complies with the required color. […]