If the blue button worked, he would let himself be captured by the Red Army, confess to everything he did, publicly denounce all his views and admit his total and utter failure as a leader. Then he'd be sentenced to death and he'd accept the verdict.

This, in turn, would just mean that all remaining nazis start simping for Rudolf Hess or some other unrepentend fascist trying to be more Hitler than Hitler. For some nazi ultras, that was already literally what happened, they glaze Hess because he didn't kill himself and never showed remorse. They do a pathetic little march to his grave every year solely because of that. You cannot fix fascism by killing or reforming one guy, no matter how much the nazis themselves believe in great man theory. If their great man lets them down, they will find a way to cope. They are nazis, disavowing reality in favor of a mythology that justifies all of their crimes and makes them feel less pathetic is the one thing these nihilist fucks believe in.

So i'd press the red button, at least then i get to be the girl who killed Hitler. The actually important question is where to find the button that makes Stalin not stop at Berlin, but that would require the US not to have nukes. Alternative history is kinda pointless tbh.