Most states have different laws regarding restrictions on the use of dimmed lights and other illegal vehicle modifications related to the color, shape, type, and location of the vehicle. Underbody lighting kits are legal as long as they remain covered and unlit on public roads and do not use or contain red or blue colors. However using lights under cars laws vary widely by state, drivers who wish to add underglow for cars should first check their state's illegal vehicle modification laws to avoid possible warnings and penalties