Cal. Vehicle Code - VEH § 25950. Section 25950.
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, except as follows:
(1)
Rear side marker lamps required by Section 25100 may show red to the front.
(2)
The color of foglamps described in Section 24403 may be in the color spectrum from white to yellow.
(3)
An illuminating device, as permitted under Section 24255, shall emit radiation predominantly in the infrared region of the electromagnetic spectrum. Any incidental visible light projecting to the front of the vehicle shall be predominantly yellow to white. Any incidental visible light projecting to the rear of the vehicle shall be predominantly red. Any incidental visible light from an illuminating device, as permitted under Section 24255, shall not resemble any other required or permitted lighting device or official traffic control device.
(4)
ADS marker lamps, as described in subdivision (i) of Section 38750, on an autonomous vehicle.
(b)
The emitted light from all lamps and the reflected light from all
reflectors, visible from the rear of a vehicle, shall be red except as follows:
(1)
Stoplamps on vehicles manufactured before January 1, 1979, may show yellow to the rear.
(2)
Turn signal lamps may show yellow to the rear.
(3)
Front side marker lamps required by Section 25100 may show yellow to the rear.
(4)
Backup lamps shall show white to the rear.
(5)
The rearward facing portion of a front-mounted double-faced turn signal lamp may show amber to the rear while the headlamps or parking lamps are lighted, if the intensity of the light emitted is not greater than the parking lamps and the turn signal function is not impaired.
(6)
A reflector meeting the requirements of, and installed in accordance with, Section 24611 shall be red or white, or both.
(7)
ADS marker lamps, as described in subdivision (i) of Section 38750, on an autonomous vehicle.
(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. Except for backup lamps, the entire effective projected luminous area of lamps visible from the rear or mounted on the sides near the rear of a vehicle shall be covered by an inner lens of the required color when the unlighted color differs from the required emitted light color. Taillamps, stoplamps,
and turn signal lamps that are visible to the rear may be white when unlighted on vehicles manufactured before January 1, 1974.