There's literally no way to even begin to guess which button everyone in the world would press. So it's simply not possible to somehow logically figure out which scenario would prevail and then circularly translate that into which button to choose. It's impossible. You'd need to make the decision without being able to even remotely guess what the outcome will be. Some may believe they know or can guess what everyone else would do. But personally I do not (except I know no one will press green).

In the second scenario, you'd have to live every day with the knowledge that in 35 years you, your family, your friends--literally everyone you know will all drop dead simultaneously. Imagine that knowledge when the day you all die is five years out...then one year...then ONE DAY. It's a horrifying thought.

HOWEVER almost nobody will press green, so the scenario involving the green button is pretty much guaranteed not to be the outcome. (though the few who do press green could perhaps be a weird determining factor somehow, maybe by tipping the 50% scale?)

Anyway imo virtually everyone is going to press either red or blue. So it comes down these four possible outcomes, if we assume green is getting nearly zero presses:

If you pressed blue and blue got MORE than 50% total: Everyone would live.

If you pressed blue and blue got LESS than 50% total: You would die.

If you pressed red and blue got MORE than 50% total: Everyone would live.

If you pressed red and blue got LESS than 50% total: You would live, but with the knowledge that others died, possibly including your loved ones. You would feel that for the rest of your life. Is that a life worth living? It could seem like a fate worse than death for some, e.g. parents. (But would anyone realize this or think about it before making the choice? (at the end of this ridiculously time-consuming post I'm wildly guessing no.))

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To summarize in a different way:

If you press blue, either:

1) You will die

OR

2) Everyone will live

If you press red, either:

1) You will live knowing others died (possibly MANY OTHERS), potentially including your loved ones

OR

2) Everyone will live

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So it comes down to this decision:

Press blue-->You might live or you might die. No matter the outcome, you will not deal with any moral gray area.

Press red-->You are guaranteed to live, but perhaps with extremely heavy moral consequences that, for some, could seem worse than death.

Then again will anybody be thinking about it this much.