For some visitor cards, a gray glass icon is used. Does this mean red or white only are valid? The symbol is not the same as blush or sparkling. Could one of those be used instead of a red or white?
I am pretty sure that the gray glass symbol is used to represent any wine. Now, if a card let you get a level 1 wine then you'd have to pick a red or white since blush or sparkling wines cannot be below a certain level. However, if a card let you discard a wine of value 4 or greater to get VPs, you could pick a level 7 sparkling if you wanted, it just wouldn't be as efficient.