Under glow laws in NJ State that putting extra lights on your car is legal. However, like many other states in the US, there are some restrictions, especially when it comes to the colors of your neon’s and how they’re displayed.
If you live in the state of New Jersey or plan on travelling there in your car, be sure to adhere to these rules when installing your under glow lights:
All lights that are displayed on the front and front sides of the car must be white or amber
Lights that are visible from the back can only be red
Your license plate lights are only allowed to be white
No cars, other than your indicators may flash or move
Just like many other states, the use of blue lights on your car are strictly prohibited as it’s reserved for emergency vehicles.
Be sure to check with your supplier for legal mode lights which comply with these restrictions.
NJSA 39:3-50. Color of lights,
All lamps and reflectors, which display a light visible from directly in front of a vehicle as authorized by this subtitle, shall exhibit lights substantially white, yellow or amber in color.(a) The color of light emitted or reflected by exterior lamps or reflectors on a vehicle shall be as follows, except as otherwise provided in paragraph (b), (c) and (d) of this section:White when the lamp is a headlamp, or spot lamp, or illuminates a license plate or a destination sign; or is located on the outside limit of a side car or other attachment on a motor cycle;Substantially white or amber when the lamp is a side-cowl or fender lamp, running-board or other courtesy lamp, front parking lamp, back-up lamp, auxiliary driving lamp; or a turn signal on or facing the front;Substantially red or amber when the lamp is a turn signal or a stop lamp on or facing the rear;Red when any other lamp or any reflector is on the rear or on either side at or near the rear, except as otherwise provided in paragraph (f) of section 39:3-61 for a combination marker lamp;Amber when any other lamp or reflector is on the front or on either side other than at or near the rear.(b) Lamps and reflectors on projecting loads shall emit or reflect light with color as provided in section 10 of this act.(c) No person shall drive or move any vehicle or equipment upon any street or highway equipped with any device or lamp thereon capable of or displaying a light of any other color than permitted by this section, except: an authorized emergency vehicle, an authorized school bus, or a vehicle authorized by a permit issued by the director.(d) A permit authorizing a vehicle to be equipped with a lamp capable of or displaying a flashing light, except as provided in 39:3-54 or a light of a color other than permitted by this section, visible from directly in front of said vehicle, may be issued by the director when necessary, in his discretion, for the reasonable and safe movement of traffic. The permit shall specify the type and color of such lamp and the conditions under which a person may drive or move the vehicle with said lamp displaying a light. The permit shall be valid only when the specifications and conditions contained therein are complied with.
The director may cancel or revoke a permit issued under authority of this section whenever the conditions for its issuance no longer exist or on any other reasonable grounds.
>>> So you definitely cannot have blue on while in motion.
Read it carefully. It says directed towards the front/back, not down at the ground. Devils in the details. I use blue all the time for underglow on my scooter. Because the lights are affixed in a way that they face down and the light can only be seen from the ground it’s not illegal. Now if you put blue lights facing forwards or backwards that’s the problems but as long as the lights aren’t facing front and back and only to the ground that’s the grey area.