Colo. Rev. Stat. § 24-72-106
In all cases in which any abstract books, copies, minutes, and extracts, purchased and placed in the county clerk and recorder's office, are admissible and shall be received in evidence under the provisions of this part 1, all deeds or other instruments in writing appearing thereby to have been executed by any person or in which they appear to have joined, except as against any person in the actual adverse possession of the land described therein at the time of the destruction of the records of said county, claiming title thereto otherwise than under a sale for taxes or special assessments shall be presumed to have been executed and acknowledged according to law, and all sales under powers, judgments, decrees, or legal proceedings, sales for taxes and assessments excepted, shall be presumed to be regular and correct, except as against said person in actual adverse possession, and unless the abstracts, books, copies, minutes, and extracts show affirmatively some defect or irregularity. Otherwise, any person alleging any defect or irregularity in such conveyance, acknowledgment, or sale shall be held bound to prove the same.
C.R.S. § 24-72-106