Many on this forum (I believe our own Jock Scot is among them) feel that diced or argyll hose are a bit much for a black-tie event, so solid colour are fine. I'm quite partial to the patterned hose, but I don't think you'd be wrong at all to wear solid hose with black tie. Claret seems to be the most popular colour with X-Markers at present, but any colour (except white and maybe black) would do the trick - just whatever tickles your fancy.

As for the shirt, my understanding when it comes to non-Highland wear is that the stiff-front shirt with detachable wing collar is acceptable for black tie, though a bit formal (and it would probably look out of place with solid-colour hose). As you said, a Marcella shirt with turn-down collar and double cuffs will do the trick just fine - and it happens to be what I have in my wardrobe for black-tie events.