(a) An artificial color may be used in a pet food only if it has been shown to be harmless to pets. The permanent or provisional listing of an artificial color in the United States Food and Drug Regulations as safe for use, together with the conditions, limitations, and tolerances, if any, incorporated therein, shall be deemed to be satisfactory evidence that the color is, when used pursuant to such regulations, harmless to pets.(b) Prior to registration of a pet food which contains additives (including drugs, other special purpose additives, or nonnutritive additives), the distributor may be required to submit evidence to prove the safety and efficacy of the pet food, when used according to directions furnished on the label. Satisfactory evidence of the safety and efficacy of a pet food may be:(1) when the pet food contains such additives, the use of which conforms to the requirements of the applicable regulation in the Code of Federal Regulations,