I have never heard of such a superstition, I have had a green K100RS bike, a green Montego estate, a green BMW525 and I have a green 4/4 4 seater, I learned to drive on a green Humber Super Snipe and a green Humber sceptre and father had two green Jaguars and a green Rover 75.
All seemed ordinary enough.
Perhaps the idea that letters written in green ink are in some way offensive may be an influence?
