Besides the lights themselves and a standard vehicle, the two other elements of this offense seem to be "carry" and "cast". Now the carry part is pretty straightforward, either they are there or not.Red and blue lights to the front restricted
(14.1) In addition to the lighting requirements in this Part, a police department vehicle may carry lamps that cast red and blue lights, but no other motor vehicle shall carry any lamp that casts red and blue lights to the front. 2007, c. 13, s. 17 (2).
But how is "cast" interpreted... does that meaning actively casting (ie. having them on) or does that mean having the capability to cast (eg. even when only used on private property)?
Not looking for legal advice, but opinion on interpretation.
If I were driving toward you and could see any other colour than white or amber, that would be an offence. Even if they are projecting down toward the ground.
If you are on private property (for a car show as per your example), then you can light it up like a Christmas tree all you want. Just don't forget to turn them off when you enter back onto the public roadway.
Besides a switch, will probably go with a relay that kills the lights once the engine is running. Don't want red and blue's behind me because I forgot to turn the front LEDs off!