Okla. Stat. tit. 47, § 156.3

A. This act, Section 151 et seq. of this title, shall not apply to and shall not be so construed as prohibiting the purchase and use of trucks or pickups by state agencies when the trucks or pickups are necessary for the performance of official duties of the state agency. B. Trucks and pickups owned and operated by the Department of Transportation shall be painted either yellow or white, and except as otherwise provided by law, shall be plainly marked with the words "State of Oklahoma" followed by the name of the department. C. The provisions of this section shall not be construed to permit the purchase of any motor vehicle of ten thousand (10,000) pounds or less gross vehicle weight. D. All acquisitions of any motor vehicle of ten thousand (10,000) pounds or less gross vehicle weight shall be approved by the Director of the Office of Management and Enterprise Services as provided for in Section 78a of Title 74 of the Oklahoma Statutes.