LED headlights are legal in CA. The question is not the type or source of light emission (LED, halogen, bulb, etc.) but the intensity and color.
"The California Vehicle Code specifically requires headlights to be clear and exhibit white light or amber, in the case of turn signals."
Any other color of headlight is illegal in California. Sometimes people will modify their vehicles with high-intensity lights, oftentimes that are blue in color and illegal.
Light output from each lamp cannot exceed 2513 lumens.