Charles ☭ 
is a GreenYou walk away from Omelas, but every other city state also has a child in a basement. All the states just use slightly different demographic criteria to pick the child.
PassengerLike a lot of people, I heard about the Omelas story before I read it, and it really shocked me that there was a big aspect of it which nobody had mentioned to me.
Le Guin uses the repeated phrase "can you imagine that?" during the story not as emphasis, but to interrogate our ability to imagine things. When she describes a blissful society and asks whether we can imagine it, she means that literally: are we able to conceptualise a place that is just nice and everyone likes it, or are we so beaten down by living in a shitty world that our brains cannot imagine anything non-shitty?
Then, when she adds the detail about the tortured child, she asks whether it's now imaginable. Does the fact that an innocent gets tortured make a paradise more believable to us? This struck me almost like a physical blow. It was a way more interesting question than I'd expected, and I really felt called out.
Then, when she talks about those who walk away, she emphasises not that they're better people or worse people, but that they're even less imaginable to us. And that was really uncomfortable.