Colo. Rev. Stat. § 23-71-514
When approved at an election held pursuant to section 23-71-502, the board of trustees, from time to time, as the proceeds thereof are needed for the purposes specified in the notice of said bond election, shall issue bonds of the district in denominations of one thousand dollars or any multiple of one thousand dollars, in its discretion, bearing interest at a rate such that the net effective interest rate of the bond issue does not exceed the maximum net effective interest rate specified in the notice of said bond election, payable at such time, determined in the discretion of the board of trustees, which bonds shall mature serially, commencing not later than five years and extending not more than twenty-five years from the date thereof. Principal and interest thereon shall be payable at such place as shall be determined by said board of trustees and designated in said bonds. Said bonds shall be made callable for redemption commencing no later than eleven years from their date in such manner, with or without premium, as may be determined by the board of trustees. Interest on local college district bonds issued on or after July 1, 1973, shall be exempt from Colorado income tax.
C.R.S. § 23-71-514