Colo. Rev. Stat. § 32-9-121
In the event that the sum produced from general ad valorem property tax levies totaling less than the maximum levy authorized by section 32-9-120(1), together with any unencumbered revenues and moneys of the district, are insufficient to pay, when due, installments on contracts and securities of the district and interest thereon and to pay defaults and deficiencies, the board shall make such additional levies of taxes as may be necessary, subject to the provisions and limitations of section 32-9-120(1), until such contracts and securities and interest thereon are fully paid. In no case shall the mill levy exceed one-half mill. No levies shall be made pursuant to this section to pay any amount of special obligations of the district payable solely from sales taxes and the revenues, or a combination thereof, of the district.
C.R.S. § 32-9-121