Colo. Rev. Stat. § 37-48-151
In addition to all other remedies for collection of assessments, including special improvement assessments, special assessments, service charges, or user fees, provided by this article, and cumulative therewith, the district may, at any time after three years after the issuance of any certificate of purchase held by the district, bring civil action to foreclose the lien for special improvement assessments, special assessments, service charges, or user fees, represented by all certificates of purchase held by the district with respect to the same land and for other relief with respect to such land as provided by the Colorado rules of civil procedure then in effect for the foreclosure of liens on real property; but no statute of limitations shall be applicable to the rights of the district arising from any special improvement assessments, special assessments, service charges, or user fees, and no decree, or sale of lands thereunder, shall be made except one subject to the lien of future unpaid installments of special improvement assessments, special assessments, service charges, or user fees. The county treasurer shall be made a party to any action of the district authorized by this section.
C.R.S. § 37-48-151