The black flags were more common in the later years than the red and white ones although any official orders I have viewed called for the red and whites. I ordered in a bunch of the decals back in the 90s and was going to apply them to the M35 I was issued and was told by my MWO not to. So although they were in the brigade orders, they were not really accepted.
The tire pressures were more commonly in black, but could just as easily be in white as well. If they were painted over an area that was cammed up in black, then they were usually painted green.
Re the markings of the BCRs, they would have been along the same lines as the rest of the armoured recce. If you are talking about the period after the early 70s, the jeep would have been in 3 color cam (with multi coats of paint liberally applied by brush), had the light recce tac signs front and rear, likely on the front fender and the back bumperette, and likely the letters BCR stencilled on the front and back.
A good source for this information would be to get a hold of the unit itself. (email
history@bcregiment.com)They often have a museum or an archive of photos which could give you what you seek. Try and look at several photos of various vehicles for an average rather than taking one vehicle as gospel . Paint and markings were done locally and often varied greatly, even between two vehicles side by side.