Earlier quoted context omitted.
The dilemma is that a lot of people will press blue so if red gets above 50% a large number of selfless but not game-theory aware people will die.
but why would anybody choose blue? there is no moral benefit to doing so. If you altered the game to say that only some fraction of the population get the choice, and everyone who doesn't get the choice is assumed blue (or, is killed if less than 50% of voters choose blue) then there's some question to be explored here. But at it stands there is literally no reason to choose blue.
Why? To contribute saving the others who chose blue. How isn't that moral?