A separate write-in ballot, which may be in the form of a paper ballot, card or envelope in which the elector places his ballot card after voting, shall be provided if necessary to permit electors to write in the names of persons whose names are not on the ballot. The ballots, ballot cards and ballot card envelopes may, at the discretion of the election authority, be printed on white paper and then striped with the appropriate colors. When an electronic voting system is used which utilizes a ballot card, each ballot card envelope shall contain the write-in form and information required by Section 16-3 of this Act.