I don't know how the law reads in Cali, but in Illinois you either have to have an amber bulb, or an amber lens. You can't run clear bulbs with clear lenses, since it's harder to see during the day. I got pulled over shortly after putting clear bulbs in mine is why I know about it.
Yeah, I'm aware of the law. A bunch of guys around here run the blued bulbs and they say that the cops don't mind. I figure...I haven't been pulled over for my flowmaster setup and the town I live in has a rule about getting a ticket if the 5-0 can hear the exhaust from 50ft. away or some shit like that.