check your vehicle registration documents. does it mention color of vehicle, if yes. color change shall be endorsed by the excise office over registration book.
If your SUV / 4x4 / 6 -8 -10 wheeler Truck / Dumper / Trailer Puller Truck is KPK registered The cabin / body change is legal after payment of nominal tax at provincial excise office.
am not sure about Balochistan, however, Punjab & Sindh does not permit such shell changes without legal payment of taxes to customs for import plus applicable provincial excise taxes