Too many of you are confusing OSHA with other safety requirements set by convention in agreement with federal funding agencies, like the U.S. Department of Justice law enforcement grants or Homeland Security funds (i.e. for police cars with lightbars). Probably the only warning lights specified in OSHA regulations are those for fork lifts, tow motors, and vehicles at industrial plants. Most emergency vehicle lighting requirements are contained within state laws.
Standards for lighting are accepted by each state and most do define colors for various authorized emergency and highway maintenance vehicles. Very few Federal agencies other than U.S. DOT set requirements for lighting, and U.S. Dept. of Transportation requirements for automotive and truck lighting are in the Code of Federal Regulations (cited under FMVSS- Federal Motor Vehicle Safety Standards). (One exception - The FAA sets standards for vehicle lighting for vehicles on the flight line on airport premises.) And, there are studies about the relative effectiveness of various lamps and colors of warning beacons. However, Society of Automotive Engineers (SAE) and other standards setting agencies (NFPA, ANSI) have significant fees to obtain the documentation.
NPS Ranger and I have been trying to tell members that the requirements and recommendations for reflective traffic vests, chevron markings, traffic cones, and to some degree, amber warning lights for highway maintenance vehicles are in the Uniform Methods for Traffic Control Devices, a document with input from several national organizations and state representatives.
Also, the United States Coast Guard sets requirements for boats and ships on navigable sea going vessels, and boats on coastal and in-land waterways
