Forget the purple dye. We need a choice of red or blue dye. Exit polling would just be a matter of counting the thumbs as they leave the polls. A coin flip on the morning of the election determines which side gets glitter in their dye. Some people will switch parties to get the glitter, rendering pre-election polls meaningless.
A federal investigation over a coin, to see whether it was flipped properly, etc., etc., etc. No thanks.
And that would be against the law. You can not give a ‘voter’ discount. I used to own and operate a movie theatre. I thought about giving a free soda to anyone that voted. Turned out, it was against the law.
And although you don’t think that it would be a problem, I’m sure there is some situation where a person who voted, doesn’t want to advertise the fact.