Colo. Rev. Stat. § 37-50-112
The board may invest any unexpended revenues of the district, including any amounts in the construction fund not needed for immediate use, to pay the cost of construction of any project, or to pay bonds or coupons or to meet current expenses, in securities meeting the investment requirements established in part 6 of article 75 of title 24, C.R.S. The board may require any revenues of the district to be deposited with such depository or bank as may be designated by the board and likewise has authority to require the treasurer of the district to take from such depository a bond with corporate surety to ensure payment of any such deposit, or to require such depository to ensure payment of any such deposit, or to require such depository to pledge securities of the same kind as those in which the district is authorized to invest its funds to ensure payment of any such deposit.
C.R.S. § 37-50-112