38300.
It is unlawful for the driver of any vehicle to disobey any sign, signal, or traffic control device placed or maintained pursuant to Section 38280.
38280.
Federal, state, or local authorities having jurisdiction over public lands may place or cause to be placed and maintained, such appropriate signs, signals and other traffic control devices as may be necessary to properly indicate and carry out any provision of law or any duly adopted regulation of such governmental authority or to warn or guide traffic.
maybe there's some section stating that yellow means advisory, I don't know, but I'd be afraid of getting a ticket for 38300
another unusual thing I've seen is when the "right lane must turn right" sign is at a significantly different location than the end of the dashed line. in Alameda, on Constitution going into the tube, the sign is ~250' before the end of the dashed line/gore point. I seem to recall reading here that once you're past the sign you're stuck in the lane, and generally the sign and paint agree as to location, but not there.