But on a more serious note, mixing formal accesories and a black suit sends a distinct message - that you know you're attending a formal function, but are trying to get away without wearing a tuxedo. I'm sorry to say, but it will come off looking a bit odd. If you are attending a black tie optional affair and prefer not to wear a tuxedo, then wear your black suit with a dressy white shirt, French cuff (cuff links) would be preferred, along with an elegant necktie. Bottom line - if you want to go formal, you have to go all the way. If you don't want to wear a tux then don't try to "cheat" by wearing formal accessories with a suit.

Accessories are far more variable - tradition suggests black accessories. If, however, you want to lighten up a bit, then red or light blue would almost work (albeit far more casual).