OSHA Safety Sign Colors and What Each Signal Word Means

What OSHA 1910.145 says about sign colors

OSHA's rule for accident prevention signs is 29 CFR 1910.145. It covers signs that indicate and define hazards, except signs designed for streets, highways and railroads. Paragraph (a)(2) says all new signs and replacements of old signs must follow its specifications, so the rule matters most when you post a new sign or replace a worn one.

The rule names three classes. Danger signs warn of immediate danger, and the design of signs posted for specific dangers must not vary. Caution signs are only for potential hazards or unsafe practices. Safety instruction signs are for general instructions about safety measures. Employers must also teach workers that Danger means immediate danger and Caution means a possible hazard.

Paragraph (d) sets the colors. Danger signs use red, black and white. Caution signs have a yellow background with a black panel and yellow letters, and any letters on the yellow background are black. Safety instruction signs have a white background with a green panel and white letters, and any letters on the white background are black.

Paragraph (e)(2) adds that sign wording should be easily read and concise, should make a positive rather than negative suggestion, and should be accurate in fact. A separate rule, 1910.144, says Danger signs shall be painted red and names yellow as the basic color for caution.

How 1910.145 relates to ANSI Z535

The color rules in 1910.145 point to ANSI color tables: the older Z53.1-1967 and the newer Z535.1-2006(R2011), which OSHA incorporates by reference in 1910.6. In a 2013 rulemaking OSHA said employers may comply with either the older ANSI standards or the newer Z535.1, Z535.2 and Z535.5 versions. OSHA repeated that point in a 2015 letter.

That same 2015 letter says an employer may use older sign designs in some parts of a workplace and newer designs in others, so there is no need to replace every sign at once. A 2011 letter, written before the 2013 rule, explains that OSHA cannot adopt a new standard through a letter and that following a newer standard with equal or greater protection may be treated as a minor issue.

One exception matters. Some OSHA standards carry their own sign wording, and those win. In the 2015 letter OSHA says asbestos regulated-area signs must follow the asbestos standard, not the ANSI Z535 design. If your hazard has its own OSHA standard, read the sign section of that standard first.

Danger, Warning and Caution: which one to use

Use Danger for an immediate hazard. OSHA's text says Danger signs indicate immediate danger. The U.S. Bureau of Reclamation, in its own facility standard, describes Danger as a situation that will result in death or serious injury if not avoided, with white letters on a red header. Live electrical gear and open pits are typical cases.

Warning sits between Danger and Caution. OSHA's tag rules let a Warning tag stand for a level between Caution and Danger, and its recommended color list gives orange for Warning. Reclamation describes Warning as a situation that could result in death or serious injury. Use it for serious hazards that are not immediate, such as guarded moving machinery.

Use Caution for potential hazards and unsafe practices, which is the job 1910.145(c)(2) gives it. Reclamation describes it as a situation that may result in minor or moderate injury, and notes it can warn against unsafe practices that damage property. Wet floors, forklift traffic and low clearance are common examples.

Choose the signal word by how serious and how close the harm is, not by the color you prefer. If you cannot tell which level a hazard falls into, ask your safety manager or a safety professional.

Notice and Safety First signs

Notice is for information that is not a hazard. OSHA's text for 1910.145 does not define it. It comes from the ANSI sign system, and Reclamation's standard uses a NOTICE header in white on a blue background for information signs, such as the name of a facility or service. Use it for rules, directions and policies, such as where visitors check in.

Safety First and general safety signs line up with the safety instruction class. Section 1910.145 describes a white background with a green panel and white letters. Reclamation uses a green header for notices of general practice on health, first aid, sanitation, housekeeping and general safety. Use green for safe-practice information, and keep it away from true hazards.

Construction sites and tags

Construction work has its own rule, 29 CFR 1926.200. It uses the same ideas: Danger signs for immediate hazards with a mostly red upper panel and a white lower panel, Caution signs that are mostly yellow, and safety instruction signs with a white background and a green upper panel. Exit signs need legible red letters at least 6 inches high on a white field.

Accident prevention tags are a different item. They attach to equipment and are covered by paragraph (f) of 1910.145, which does not apply to construction or agriculture. Tags use the signal words Danger, Caution or Biological Hazard, and the word must be readable from at least five feet. Biohazard signs have their own paragraph, (e)(4).

Choosing and ordering safety signs

Our safety designs use Danger (red), Warning (orange), Caution (yellow), Notice (blue) and Safety First (green) headers in the ANSI Z535 header style. Start with custom safety signs, then look at high voltage signs, hard hat area signs, flammable signs, PPE required signs and Safety First signs. The full range is on the safety signs page.

Every sign can carry your own line of text, so you can name the exact hazard or rule in plain words. This guide explains the rules and is not legal advice. Your hazard assessment, the OSHA standard for your specific hazard, and your state and local rules decide what you must post, so check them or ask a safety professional.

Common questions

Sources

• 29 CFR 1910.145, Specifications for accident prevention signs and tags (eCFR)
• 29 CFR 1910.144, Safety color code for marking physical hazards (eCFR)
• 29 CFR 1926.200, Accident prevention signs and tags (eCFR)
• OSHA letter of interpretation, October 13, 2015 (ANSI Z535 and warning signs)
• OSHA letter of interpretation, February 22, 2011 (newer ANSI sign standards)
• Bureau of Reclamation Safety and Health Standards 1.08, Signs, Signals, and Barricades (2024)

This guide explains the rules in plain words; it is not legal advice. We read the sources above on October 24, 2026. Rules change and many are set by your state or city: check the current text, or ask your local code official, before you rely on it.