49 C.F.R. § 172.440
RADIOACTIVE YELLOW-III label
(a) Except for size and color, the RADIOACTIVE YELLOW-III label must be as follows:

(b) In addition to complying with § 172.407, the background color on the RADIOACTIVE YELLOW-III label must be yellow in the top half and white in the lower half. The printing and symbol must be black, except for the “III” which must be red.