The hazardous material identification numbers must be displayed on portable tanks, cargo tanks, and other bulk packaging. The regulations require black _______ numbers.

You must display the identification number of the hazardous materials in portable tanks and cargo tanks and other bulk packaging (such as dump trucks). Identification numbers are in column 4 of the Hazardous Materials Table. The rules require black 100 mm (3.9 inch) numbers on orange panels, placards, or a white, diamond-shaped background if no placards are required. Specification cargo tanks must show re-test date markings. [Commercial Driver’s License Manual]