It's not as easy to label as halal food, as there are different
kinds of vegetarians. Some eat eggs, milk and even seafood, while
others are vegans.
Then they can make various signs. For example they can label one as
vegan, one as lacto-vegetarian, ovo-vegitarian, lacto
ovo-vegetarian. (google them if u dun noe what they mean). Then the
people can choose what they can eat.