I think that in the sixties, 'Marina Blue' was so popular, probably every manufacturer had to duplicate it... I suspect it will always be a popular color, regardless of what name they assign to it..
PS. In case it didn't come thru with my post re the Mopar crazy colors, My opinion on the Chevrolet Royal Plum is that it is a MUCH more classy color than the Mopar Plum Crazy (which sorta slaps you in the face)... Royal Plum is one of those colors that also will always looks good and current.