21 C.F.R. § 73.40
(a) Identity.
(b) Specifications. The color additive shall conform to the following specifications:
Volatile matter, not more than 4 percent. Acid insoluble ash, not more than 0.5 percent. Lead (as Pb), not more than 10 parts per million. Arsenic (as As), not more than 1 part per million. Mercury (as Hg), not more than 1 part per million.