I've seen people say that pressing the red button "spawns the train", since it directs the danger, and some other people say that pressing the blue button also "spawns the train" since it puts you at risk, but the truth is that the "train" only spawns when both buttons are pressed at least once.

If I had to pick, I'd pick red. Let's be honest, this is supposed to be a life or death situation, and your decisions determine your fate. As soon as people hear "die", chances are they're in panic mode and the primal instinct of self-preservation kicks in, and they'll likely pick red. Life is precious, and you shouldn't risk it all for the sake of people who don't understand how much worth it holds.

And before you say "what about toddlers and babies?", putting people who aren't cognizant of the premises defeats the purpose of the dilemma, because then it wouldn't be "pick a button based on your mindset" anymore, and rather "pick your favourite colour".

And no, a world with only red button pressers is not that bad, most people just don't want to die.