So I spent an hour looking through the vehicle code for CA on DMV's website.
I couldn't find anything that specifically forbade darkened housing.
Only thing I could find was that various lights and reflectors must be visible from certain distances when in use.
So I'm wondering now if getting smoked lenses is fine if you get bulbs strong enough to meet the visibility requirements.
Let me give some links so if anyone is inclined, they could maybe see something I missed.
Vehicle Code on DMV Website
All of these are under:
- Division 12 - Equipment of Vehicles
- Chapter 2 - Lighting Equipment
Article 2 - Headlamps and Auxiliary Lamps -
link
Headlamps - V.C. 24400
- Doesn't mention visibility.
Article 3 - Rear Lighting Equipment -
link
Taillamps - V.C. 24600
- Light must be red.
- Must be visible from 1,000 feet.
Stomplamps - V.C. 24603
- Light must be red.
- Must be visible from 300 feet.
Backup Lamps - V.C. 24606
- Light must be white.
Reflectors on Rear - V.C. 24607
- Must be visible from 350 feet.
Article 5 - Signal Lamps and Devices -
link
Visibility Requirements of Signals - V.C. 24952
- Turn signals must be visible from 300 feet.
Article 6 - Side and Fender Lighting Equipment -
link
Clearance and Side-Markers - V.C. 25100- Front clearance light must be amber, back must be red.
- Both visible from 500 feet.
- Side markers also must be visible from 500 feet.
Article 15 - Light Restrictions and Mounting -
link
Color of Lamps and Reflectors - V.C. 25950
- Seems to just say what colors certain types of lights should emit.