Colo. Rev. Stat. § 30-26-302
The board of county commissioners, when authorized as provided in section 30-26-301, may make and issue coupon bonds of the county not exceeding the amounts authorized by the electors, payable at the pleasure of the county but absolutely due and payable twenty years after such date, bearing interest at a rate such that the net effective interest rate of the issue of bonds does not exceed the maximum net effective interest rate authorized, payable annually or semiannually; such interest and principal, when due, shall be payable at the office of the county treasurer of the county or at such other location as the board of county commissioners may designate. The board of county commissioners shall prescribe the form of said bonds and the coupons thereto; and, to provide for the principal and interest and redemption premiums accruing on the bonds, it shall provide for the levying of a tax which, together with such other revenue, assets, or funds as may be pledged, will be sufficient to pay the principal, interest and redemption premiums, if any, accruing on the bonds.
C.R.S. § 30-26-302