Colo. Rev. Stat. § 38-41-116
No action or proceeding whatsoever shall be brought or maintained by any person to enforce or procure any right or title accorded to the purchaser under any contract for the purchase and sale of real property if such person is not in possession of the real property described in and the subject of such contract of purchase and sale unless such action or proceeding is commenced within ten years of the day or the happening of the event appointed in said contract for the delivery by the seller of a deed of conveyance of the property therein agreed to be purchased and sold. If no day is appointed in such contract for the delivery of such conveyance, then such action or proceeding shall be commenced within ten years of the day on which the last and final installment of the purchase price would have been paid but not thereafter.
C.R.S. § 38-41-116