from the HTA:
73. (1) No person shall drive a motor vehicle upon a highway,
(a) with any sign, poster or other non-transparent material or object placed on the windshield or on any window of such motor vehicle; or
(b) with any object placed in, hung on or attached to the motor vehicle,
in a manner that will obstruct the driver’s view of the highway or any intersecting highway. R.S.O. 1990, c. H.8, s. 73 (1).
Colour coating obstructing view prohibited
(2) No person shall drive a motor vehicle upon a highway where the surface of the windshield or of any window of the vehicle has been coated with any colour spray or other colour coating in such a manner as to obstruct the driver’s view of the highway or any intersecting highway. R.S.O. 1990, c. H.8, s. 73 (2).
Colour coating obscuring interior
(3) No person shall drive on a highway a motor vehicle on which the surface of the windshield or of any window to the direct left or right of the driver’s seat has been coated with any coloured spray or other coloured or reflective material that substantially obscures the interior of the motor vehicle when viewed from outside the motor vehicle. R.S.O. 1990, c. H.8, s. 73 (3).
Nice and vague eh?