Depends on which state your're in.
Down here, yellow cabs are actually cab yellow. Having said that I've seen at least 100 different shades of cab yellow.
A very good mate is a full time panel beater / spray painter for a cab company.
I guess before the taxi reforms of many years ago, they could be any colour. I can't remember if Silvertop had silver roofs painted, but I think it changed with the yellow around the EB falcon '94ish?
