Answer to Question #232 Submitted to "Ask the Experts"

Q

Do the colors magenta and yellow have any significance when used in the radiation warning symbol?

A

A chapter in the book Health Physics: A Backward Glance, edited by Ronald L. Kathren and Paul L. Zeimer, 1980, explains the choices of the colors that are now so familiar to us. In that chapter, Lloyd D. Stephens and Rosemary Barrett explain how the "20th Century Danger Sign" was selected in 1949. They stated, however, that "of more concern than the symbol itself, there was a rather lengthy discussion on the choice of colors to be used. Briefly, the magenta color was readily accepted as being of unique color. The background was selected originally as a light blue, being the remaining color after eliminating colors used in engineering codes frequently used in a laboratory or shop. Eventually, the high visibility yellow was accepted by common assent." The authors added that "this symbol is now formalized in the Federal Regulations Title 10, Part 20. It has been carried to the farthest reaches of earth, onto our nearest celestrial neighbor, the moon, and even today is traveling on a cosmic journey into the unknowns of the universe. Truly, here is a '20th Century Danger Sign'." Thank you for asking about the history of the colors of this symbol.

Gen Roessler, Editor HPS website