Colo. Rev. Stat. § 24-105-302
Every contract modification or contract price adjustment under a construction contract with the state in excess of an amount specified in the contract shall be subject to prior written certification by the controller or other official responsible for monitoring and reporting upon the status of the costs of the total project or contract budget as to the effect of the contract modification or adjustment in contract price on the total project or contract budget. In the event that the certification of the controller or other responsible official discloses a resulting increase in the total project or contract budget, the procurement agent shall not execute or make such contract modification or adjustment in contract price unless sufficient funds are available therefor or the scope of the project or contract is adjusted so as to permit the degree of completion that is feasible within the total project or contract budget as it existed prior to the contract modification or adjustment in contract price under consideration; except that, with respect to the validity of any executed contract modification or adjustment in contract price which the contractor has reasonably relied upon, it shall be presumed that there has been compliance with the provisions of this section.
C.R.S. § 24-105-302