Colo. Rev. Stat. § 30-26-105
The board of county commissioners is authorized to prescribe the form of such bonds, and the coupons thereto, and to provide for the half-yearly interest accruing on such bonds actually issued and delivered; they shall levy annually a sufficient tax to fully discharge such interest; and, for the ultimate redemption of such bonds, they shall levy annually, after nine years from the date of such issuance, such tax upon all the taxable property in their county as shall create a yearly fund equal to ten percent of the whole amount of such bonds issued, which fund shall be called the redemption fund. All taxes for interest on and for the redemption of such bonds shall be paid in cash only and shall be kept by the county treasurer as a special fund to be used in payment of interest on and for the redemption of such bonds only; and such taxes shall be levied and collected as other taxes.
C.R.S. § 30-26-105