There are so many levels to this, it's fascinating. I just wish the buttons weren't red and blue, because that immediately puts this in a political frame in the U.S.
Everyone in the world has to take a private vote by pressing a red or blue button. If more than 50% of people press the blue button, everyone survives. If less than 50% of people press the blue button, only people who pressed the red button survive. Which button would you press?