Colo. Rev. Stat. § 37-90-127
As the terms of the members of the board of directors expire, their successors shall be nominated by petitions containing the signatures of not less than fifteen percent of the number of qualified taxpaying electors of the division who voted at the last preceding district election, to be filed with the secretary of the district not less than thirty-five days before the election; thereafter, the members shall be elected for terms of four years by the plurality vote of the taxpaying electors of the division of the district which they represent. Such elections shall be held on the first Tuesday in February preceding the expiration of such terms and shall be conducted by the district board in the general manner prescribed in section 37-90-124.
C.R.S. § 37-90-127