Most state laws say red to the rear, white displayed forward with amber used and turn signals. bicycle laws would be regulated by the state and in some cases per the city you live in sometimes.

BUT according to the California Bicycle Safety Co and California Bike Org:


Lights: At night a white headlight visible from the front must be attached to the bicycle or the bicyclist. CVC 21201(d) and CVC 21201(e)

Reflectors: At night bicycles must have the following reflectors:

1. Visible from the back: red reflector. You may attach a solid or flashing red rear light in addition to the reflector.
2. Visible from the front & back: white or yellow reflector on each pedal or on the bicyclist's shoes or ankles
3. Visible from the side: 1) white or yellow reflector on the front half of the bicycle and 2) a red or white reflector on each side of the back half of the bike. These reflectors are not required if the bike has reflectorized front and back tires. CVC 21201(d)

From the California DMV website:
http://www.dmv.ca.gov/portal/dmv/?1d...t_facts/ffdl37

Nothing says you can not have a different colored lights but being it pretty much says you must follow vehicle laws otherwise stated I am assuming its not allowed. Although I am sure no LEO probably cares short of getting a complaint.