There are special "Black Diamonds"...
http://en.wikipedia.org/wiki/Carbonado
Also, "Black" cards were the exclusive super elite cards long time ago like the Amex Centurion when it was introduced and the waiter picked it up with a lot of respect at the time when you placed it on the table
So I'm not against a black card or black in combination with Diamond - even though I think it is not a good match - but I think the cards just look incredible cheap.
Anyway, did anyone receive a Diamond SmartPass?