NOTE: “Red presser” and “blue presser” refer to what you would press in the deadly version. If you secretly choose the marking version, you may still press either button afterward, knowing no one will die.

A malevolent djinn informs you that he is going to run the red-vs.-blue button test on humanity:

“You, and all other humans, have a red button and a blue button before you. Each eligible person must press one button. If over half of the people with the mental capacity to understand and make this choice press the red button, all blue-button pressers will die. Otherwise, nothing will happen.”

However, you will secretly be given a choice about whether the djinn runs the deadly version, the classic version described above, or a marking version.

In the marking version, the djinn makes the same claim as in the deadly version. Everyone except you sincerely believes the deadly version is being run. But the djinn is lying to them: it will not kill anyone, regardless of choice. Instead, every person who makes the choice is indelibly branded with a mark indicating which button they pressed. The mark cannot be removed, hidden, or obscured by any means or loophole a human mind can conceive of, and it is universally legible. Those who were mentally unfit to make such a choice, and those not yet born, will be unmarked. Only the choice is recorded, not motives, reasoning, confidence, fear, confusion, or any other context. Everyone knows afterward that the marking version was run: the djinn never would have killed anyone, but everyone made their choice believing the deadly version was real. The djinn declines to predict the consequences of this, leaving you to predict their shape and scale from your own priors.

Assume you have irrefutable proof that, for all its willingness to deceive humanity, the djinn is not deceiving you and will honor your decision. Either way, the button choice will be presented immediately afterward, with no opportunity for discussion or collusion.