I think it's fascinating that Grendel-13 and Aizek have the reactions to this film that they have stated below, and would bet anything in my wallet that they're both under 30 years old.
This film was/is a parable. At the particular time it was created, it was a parable about the budding Cold War, and about the immediately past Holocaust. The focus was on the problem that having a difference, one not even chosen, should destroy one.
That had destroyed six million Jews in the Second World War, and the film was partly about that. It had also begun to destroy people in America who thought that Communism might have something to offer.
And, very directly, it had by virtue of the Second World War's very existence, destroyed the parents of thousands and thousands of children worldwide, even including some of those in the USA. Hatred based on no sensible matter had orphaned thousands in the USA, to put it directly.
And what damn difference should it make if some kid's hair was all of a sudden green? (Interestingly, many kids nowadays have by their own choice and the miracles of modern dye technology, green hair -- but nobody could do so in 1948 without Divine intervention -- which was the ultimate point of the film, which the kids don't realize.) In that era, it made the difference that the youngster was "different." Being "different" back then was a Bad Thing to the majority.
Not just an oddity.
A Really Bad Thing. A Bad Thing Bad Enough to cause Execution. Literally. I was alive then. I saw this film when it came out. It was an audacious film, a film ahead of its time.
This kind of stuff really and truly happened in the USA, Constitution be damned. Yes, it was a metaphor, but it has to be understood in the context of the times.
Someone mentioned cross-dressing. That is completely unrelated, and is illustrative of a lack of understanding of the lesson of history that was being dealt with in the movie. The difference is one that is noticeable, inborn, and yet insignificant, like, to be pedantic, being Jewish. Cross-dressing is a choice; one may believe that the desire to do it is inborn, but the choice to give in to that desire is one made by the individual.
There is no choice to be Jewish by birth -- or to be suddenly given Green Hair by Providence.
And the consequences of a person's having a basic characteristic given by God are chosen by Man. Thus, we choose to kill six million Jews, or let them be killed. We also choose to treat someone who suddenly, by no choice of his own, turns up with green hair, as we choose to treat him.
This is a really major film in the context of its time, and I must admit that it irritates me to see people who have no idea what they're talking about, since they haven't taken the trouble to learn about the context, say things about it that are just irrational.
Sorry. But not very.