And where in the original post is specified who does "the murdering"? As far as I see blue pressers are explicitly putting themselves in harms way and red pressers have fuck all to do with it.
Just because someone jumped infront of the train and died doesn't mean the conductor is a murderer.
The red pressers commit murder. If people don't press red, the blue pressers don't die.
Train conductors and companies take reasonable precautions to avoid killing people - they aren't indifferent to it. If they just built tracks and started running trains on them without taking measures to avoid mowing people down they absolutely would be guilty of murder.
For it to be murder it would need to be unlawful (lets just assume this entire hypothetical is unlawful) and planned, so unless red pressers are specifically doing it to kill blue pressers it is factually not murder. Blue pressers have put themselves into the situation of possibly dying, which was entirely their choice and isn't the responsibility of anybody else (ignoring the "forced to press a button by some mystical force/being").
There is a reason why even "duty to rescue" laws usually do not require the rescuer to endanger themselves doing it, which in this case would most certainly be the case (going from 0% of death to "who knows, this is entirely out of my control but non-negligable chance of dying" % of death).
> If they just built tracks and started running trains on them without taking measures to avoid mowing people down they absolutely would be guilty of murder.
Most stations in the world do not have any guardrails to the tracks themselves. If someone decides to walk onto them as the early end of a station they will most likely die if the train is arriving. The tracks were there, the train was scheduled just the person decided to put themselves into harms way. At most it would be considered manslaughter.
A single button labeled "Murder" appears out of nowhere appears, and if more than the majority of people press it, then the people who didn't press will die.
I'm pretty sure most people would just ignore and keep going with their day since why would everyone in the world be so cheesed to press the murder button?
Anyways, these are all reductive scenarios once outside of game theoretics (like this one partially is) - I find this ragebait question really funny because every minor reframing shows significant biases in how you map the theory of mind for the public, and makes the reductive question entirely different.
The framing leads many people to pick blue for its altruistic framing. Enough, in fact, that 50% quorum is honestly not difficult. A lot of red-advocates seem to have a False Consensus Effect going where they're convinced way more people than in reality will interpret this "dilemma" as "do you step in the human grinder in hopes of jamming it", and act accordingly.
A 70% or 90% requirement, or just explicitly framing it as "do you step into the human grinder" would make it vastly easier to aim for 100% red, but we're dealing with the literal words of the "everyone lives button" here.
Except we all chose red because its the obvious choice and now you are dead.