Colo. Rev. Stat. § 37-50-115
In addition to all other remedies for collection of assessments provided by this article, 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 assessments 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. No statute of limitations shall be applicable to the rights of the district arising from any assessment. No decree, or sale of lands thereunder, shall be made except one subject to the lien of future unpaid installments of assessments. The county treasurer shall be made a party to any action of the district authorized by this section.
C.R.S. § 37-50-115