Colo. Rev. Stat. § 31-10-807
In municipalities using an electronic voting system, the clerk shall distribute to the election judges in the respective precincts a sufficient number of ballots. The ballots shall be sent in one or more sealed packages for each precinct with marks on the outside of each stating clearly the precinct and polling place for which it is intended, together with the number of ballots enclosed. Such package shall be delivered to one of the judges of election of such precinct between the close of business on the Friday preceding election day, or during any earlier day in which a judges' school of instruction is held, and 8 p.m. on the Monday before election day. A receipt for the ballots thus delivered shall be given by the election judge who received them. The receipt shall be filed with the clerk, who shall also keep a record of the time when and the manner in which each of said packages was sent and delivered.
C.R.S. § 31-10-807