According to the National Road Traffic Act, vehicles displaying a red or blue light (or a combination thereof), have absolute right of way - when it’s safe to do so. Whether or not you trust the legitimacy of the vehicle, it is advisable that you give way as best as possible. In light traffic situations, this can simply be done by pulling over, but in high-congestion scenarios, your best bet is to nudge your car as far over to the verge as possible, without causing any danger to yourself or other motorists.
Remember that it’s not for drivers to decide whether or not a vehicle is a legitimate government or emergency vehicle. Should you feel like the official vehicle is acting outside its legal bounds, your best bet is to jot down the number plate and report the car to the relevant authorities.