I think a black discus with some blue or orange would look really striking. I always wondered why people dislike the blue x pigeon crosses or heavily peppered pigeons because some of those with a lot of black might look very interesting and maybe produce something like an almost-black discus if combined selectively? Maybe even solid blacks? I have one like that and colour-wise he's my favourite. I could easily imagine a similar fish with more black becoming popular.
Attachment 139708 Attachment 139730
/edit... sorry for changing the pics... the colour changes so much depending on lighting, it's hard to get a good picture of his "real" colour. he's usually a bit darker and the bars don't show except occasionally.