The American National Standards Institute has identified specific "safety" colours for industry. These colours mark equipment, have specific meanings and uses, and mark safety signs in specific configurations.
Industry Color Standard
The Occupational Safety and Health Administration and ANSI have a generalised colour code for industry. The National Fire Protection Association, U.S. Department of Transportation and others all recognise colour coding for specific signage or placards, but it is all based on the ANSI Z535 Safety Alerting Standards.
Red and Orange
Red and orange indicate danger. Red indicates fire protection equipment, alarm boxes and extinguishers, and emergency shutoff switches on machinery. Orange marks dangerous parts of machinery, so anything that cuts, crushes, pinches or will cause injury should be orange.
Yellow and Black
Yellow indicates caution and is used to mark hazards. Storage cabinets for paints, gasoline cans, other flammable liquids and explosives are yellow. Yellow and black together bring attention to a particular hazard by being visually striking.
Green is the colour of safety. Personal protective equipment, first-aid kits, eyewash and emergency shower locations are marked in green.
Blue is widely used in railroad operations to indicate a warning. In general industry, blue is used to provide information. Information signs have a blue background with white lettering and symbols.
Even though ANSI has provided a colour code for industry, it is not a mandatory standard. Specific trades and safety organisations may have their own colour codes.