I recently purchased a very dark navy Zegna tuxedo. I've been told that this shade of blue can actually look darker than the deepest blacks under indoor lighting. Does anyone have suggestions on what color bow-tie and cummerbund I should pair with it? Should I be looking for a similar dark navy set? Or will a traditional black set work fine?
I think you actually must mean midnight blue, which is an elegant alternative to black for a tuxedo. Many midnight blue tuxedos come with black lapel facings. In that case, black should be the obvious color for the bowtie and cummerbund. If the lapel facings are midnight blue, I personally would go with the same color for the bowtie and cummerbund although these items are not nearly as readily found as their counterparts in black.
Match the lapels like the Capn said. Although, if the lapels are midnight blue, then you can use black.
I'm not big on crazy bowties or cummerbunds but I can tolerate a bold or wild vest. Usually in silk and I have seen many in online UK wedding shops.
I have a bright red version of my rabbit silk that I may do into a vest for black tie.