by all means, its legal to own or paint your airsoft black as long as the cop dun see it, and no one complain about it... it just not a good idea to...!!
because i checked with my local firearm officer, they are OK with clear, or frosted white receiver
however even the canadian tinted ones, they will consider it as realistic, which means, if you holding on to it and somehow have the barrel pointing to a officer, they WILL SHOOT
and for the canaidan, we dun need orange tip, its for u.s.
at last, for any traveling outside your house, please do use a box or bag so no one see it
hopes this help