Colo. Rev. Stat. § 23-71-523
All outstanding bonds and all acts and proceedings had or taken, or purportedly had or taken, prior to July 1, 1964, by or on behalf of any district under law or under color of law preliminary to and in the authorization, execution, sale, issuance, and payment of all such bonds are validated, ratified, approved, and confirmed, notwithstanding any lack of power or authority or otherwise, other than constitutional, and notwithstanding any defects and irregularities, other than constitutional, in such bonds, acts, and proceedings and in such authorization, execution, sale, issuance, and payment, including, without limiting the generality of the foregoing, such acts and proceedings appertaining to bonds, all or any part of which have not been issued nor purportedly issued.
C.R.S. § 23-71-523