California Code, Vehicle Code - VEH § 21457

(a) Flashing red (stop signal): When a red lens is illuminatedwith rapid intermittent flashes,a driver shall stop at a clearly marked limit line, but if none, before entering the crosswalkon the near side of the intersection, or if none, then at the point nearest the intersecting roadway where the driver has a view of approaching traffic on the intersecting roadwaybefore entering it, and the driver may proceed subject to the rules applicable after making a stop at a stop sign.

(b) Flashing yellow (caution signal): When a yellow lens is illuminated with rapid intermittent flashes,a driver may proceed through the intersection or past the signal only with caution.