(b) In addition to complying with § 172.519, the background color on the DANGEROUS WHEN WET placard must be blue. The letters in the words “WHEN WET” must be at least 25 mm (1.0 inches) high. The symbol, text, class number and inner border must be white.
[Amdt. 172-123, 56 FR 66263, Dec. 20, 1991]