Red– must be used for fire-related hazards and emergency switches, bars, and buttons on hazardous machines.
Yellow– must be used for indicating caution, as well as physical hazards, including striking against, stumbling, falling, tripping, and “caught in between.”
Meanwhile, the ANSI Z535 safety sign standard provided 10 safety colors for visual communication, each with specific applications. Here's a brief rundown of the most common colors, what they mean, and where to apply them.
Red– recognized for identifying the most serious hazards, as well as fire hazards and fire equipment. Used for “Danger” signs and labels that warn when death or serious injury.
Yellow– recognized for communicating hazards that may lead to worker injuries if not avoided—usually used for signs and labels that warn against unsafe practices.
Orange– recognized for dangerous machines or equipment that may crush, cut, shock, or injure workers. Used for color coding “Warning” signs and labels when a hazard may cause death or serious injury but not enough to warrant a "Danger" notice.
Green– recognized for general safety signs. Used for safety-related messages that don’t touch on specific workplace hazards.
Blue– recognized for communicating information unrelated to personal injuries and other hazards, or most commonly on “Notice” signs. Often used for maintenance work and other safety precautions signs.