49 C.F.R. § 172.417
FLAMMABLE GAS label
(a) Except for size and color, the FLAMMABLE GAS label must be as follows:

(b) In addition to complying with § 172.407, the background color on the FLAMMABLE GAS label must be red.
(a) Except for size and color, the FLAMMABLE GAS label must be as follows:

(b) In addition to complying with § 172.407, the background color on the FLAMMABLE GAS label must be red.