I live in California. I have the Serfas TL-LB5 LED taillight, which has 3 red LED's in the middle and 1 white LED on either side of the red for a total of 5 LED's. A friend has the same light. We bought these at the LBS. Yesterday a young (rookie?) cop told her she could only have a red taillight, not red and white. I Googled "California bicycle law" and didn't find anything about red and white being illegal. The only restricted light color in CA is blue.
Here's the link to the light on Serfas' website: http://www.serfas.com/product.asp?ProductID=308
I use mine on my recumbent along with a Planet Bike Superflash and a Lightman amber LED flasher. If the red and white is going to be a problem I'll replace the Serfas with another Superflash, which is brighter anyway.