Flusser opines that shoes in leather other than black or brown looks fake and contrived (they "never connoted much class or taste" and are "stylishly sophomoric" and are never appropriate unless they're in suede or velvet "in such status-conferring classics as the Gucci buckled slip-on, Belgian loafer, or Prince Albert dress slipper" -- Style and the Man, p. 42), and Manton obviously agrees with him. I don't. I happen to like good burgundy leather, even leather that's not shell cordovan. Heck, I even have seen green shoes that I like. Navy shoes, either in smooth or grained leather or in suede, can be stunning. It would be a bit silly to make them the backbone of your shoe collection, but there's nothing wrong or tasteless about having a pair or two. I might wear a navy suede Prince Albert slipper with a midnight blue tuxedo (although I would more readily opt for scarlet suede), but I don't think that I would wear navy suede cap-toes with a suit. Something more casual would be more appropriate.