The instructions appearing on the ballot shall describe the appropriate mark to be used by the voter. The mark shall be consistent with the requirements of the voting system in use in the precinct. The voting mark used on paper ballots may be a cross or check which shall be placed in the voting targets opposite the names of candidates. The fact that the voting mark is made by an instrument other than a black lead pencil shall not affect the validity of the ballot unless it appears that the color or nature of the mark is intended to identify the ballot contrary to the intent of section 39A.4, subsection 1.