2 Colo. Code Regs. § 601-10-4.22
The Contract must be executed on behalf of the Low Responsible and Responsive Bidder by an Individual with legal authority to bind the Low Responsible and Responsive Bidder. Such an Individual includes the owner of a sole proprietorship, one or more partner members of a partnership, one or more authorized members or officers of each firm representing a joint venture, the president or vice-president of a corporation, or an authorized agent of the Contractor. Anyone signing as agent for the Low Responsible and Responsive Bidder must file with CDOT written evidence of such authority. The Contract shall be returned, together with the Contract Bonds, within fifteen calendar days after the date of Award unless otherwise specified by CDOT. If the Contract is not executed by CDOT within thirty calendar days from date of Award, the Low Responsible and Responsive Bidder shall have the right to withdraw its Bid without penalty, provided the Contractor returned the executed Contract and bond within fifteen calendar days from the date of the Award. No Contract shall be considered effective until it has been fully executed by all of the parties thereto.
2 CCR 601-10-4.22