Mont. Code Ann. § 13-21-212

Ballots mailed to a covered voter must be handled as prescribed in 13-13-214, except that both the envelope in which a ballot is mailed to the covered voter and the signature envelope for the ballot must have printed across the face the information and graphics and be of the color prescribed by the secretary of state consistent with the regulations established by the federal election commission, the U.S. postal service, or other federal agency.