(a) An artificial color may be used in any pet food or specialty pet food only if it has been satisfactorily shown to be harmless to pets or specialty pets, as the case may be. The permanent or provisional listing of any artificial color in the Federal 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 or specialty pets.