Well, the Italian Mezzo tight is not a stroller so different rules apply I guess - anyhow in the rest of the world, if you want to use a odd waistcoat for a wedding, wear it with a morning suit - also there are no substitutes for the black tie and the cashmere (striped) trousers to be worn with a Stroller ( or Black jacket ( hence no grays either) as it is known i the UK)
However, as has been previously noted - almost nobody will know, and consequently care!
As for the Truman wedding, I'm afraid our american cousins as it were, are perhaps not the most likely source in these matters
I do not know where you get this "truths". The word for stroller/stressman is mezzo tight (or tait) in Italian. You may be referring to a quick google search that bring back RTW ceremony options, mostly showing "d'orsay" type coats. Better examples (first from a sartoria=bespoke):
Also Oxford grey is an accepted colour for morning coat and stroller in most countries
Well, where do you think i get them?
Any expert can confirm - if you can find one!
As indicated above, i am not familiar with Italian ways.
One shall distinct between strollers and morning coats - the latter can of course be worn in grey for certain occasions - the stroller, however, is akways black.