N.H. Rev. Stat. Ann. § 266:78-f

Law enforcement officers, state probation and parole officers, and state correctional officers in the performance of their official duties shall only illuminate emergency lights and warning lights when in pursuit or stopping a violator, when responding to but not returning from an emergency call for service, when conducting an escort, or when parked on or adjacent to the highway to warn other traffic of a hazard or obstruction. Except as provided for under RSA 266:78-b, II, no person other than a sworn law enforcement officer, state probation and parole officers, and state correctional officers in the performance of their official duties shall drive a vehicle with a blue light or lights in operation.