1. Danger signs – Indicate immediate danger and alert personnel that special precautions are necessary. OSHA specifies that red, black and white colors are to be used for danger signs.
  1. Caution signs – Warn against potential hazards or caution against unsafe practices. OSHA specifies that caution signs must have a yellow background and black panel with yellow letters. All letters used against the yellow background must be black.
  1. Safety instruction signs – Must be used where there is a need for general instructions and suggestions relative to safety measures. OSHA specifies that safety instruction signs must have a white background, green panel and white letters. Any letters used on the white background must be black.

In the fall of 2013, OSHA endorsed the latest best practices related to safety signs by referencing the 2011 ANSI/NEMA Z535 safety sign and tag standards in its regulations.