Midnight Oil is quite dark (with a deep red cast in full sun) but doesn't grow well for me. Coal Seams is a very very dark purple/black and is a champion grower. Very pretty blooms too. I love Black Lightning. It photographs lighter than it really is, but is very pretty in the garden. I don't really grow any other black selfs, and I have never seen any that are just true black. That said, I have two on order - Black Olive, another dwarf, and AmpItUp which is deep cherry black.
