Hazard Colour Coding

What it is

Warning signs combine a signal word with a colour. The idea of hazard colour coding is that the colour carries a level of danger so that a reader can take in the level at a glance. Whether people share the same graded reading of the colours is an empirical question, and Chapanis put it to raters.

In effect

Chapanis asked people to judge the hazard associated with three signal words, CAUTION, WARNING and DANGER, each combined with four background colours: white, yellow, orange and red. DANGER was perceived as the highest level of hazard, WARNING an intermediate level and CAUTION the lowest, with the greatest consistency for DANGER. There was a small but significant amount of disagreement about the relative hazard of CAUTION and WARNING. The four colours were perceived as successively greater levels of hazard in the order white, yellow, orange, red. The greatest consistency was found for DANGER on a red background, and there was little agreement about the best colours for CAUTION and WARNING. Ratings of the seriousness and probability of injury placed CAUTION and WARNING much closer to each other than to DANGER.

In those ratings yellow sat one step above white and one below orange. That is a graded tendency in one set of ratings and not a fixed code.

What it does not say

The study rated signs. It did not test brands, packaging or advertising, and it does not show how a yellow brand mark is read when it appears beside safety messages. The article Yellow in Branding: Optimism, Attention and Risk draws the cautious inference that yellow sits at the mild end of a warning scale where it appears beside such messages, and marks that step as its own reasoning.

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