Washington Revised Code Title 46. Motor Vehicles § 46.37.196. Red lights on emergency tow trucks--Rear facing blue lights

All emergency tow trucks shall be identified by an intermittent or revolving red light capable of 360 degree visibility at a distance of 500 feet under normal atmospheric conditions. The emergency tow trucks may also operate rear facing blue lights for use only at the scene of an emergency or accident. The red lights may be used when the tow truck is reentering the roadway from the scene of an emergency or accident for a reasonable distance to reach operating speed from the scene, and the combination of red and blue lights may be used only at the scene of an emergency or accident. It is unlawful to use the combination of lights when traveling to or from the scene of an accident or for any other purpose.