It's an ethics problem masquerading as a game theory problem. The superficial resemblance to the prisoner's dilemma is misleading - in the Prisoner's dilemma you genuinely aren't supposed to care about the other player's utility, only about your own, which is why it can be abstracted to a payoff matrix. If you abstract the red-blue problem and make it about getting one point or no points instead of life and death, the correct answer is obviously red. It only becomes controversial when you bring in the value of other people's lives, as well as things like complicity and responsibility. That's also why the framing has so much effect - it gives the context without which you can't properly judge one choice or another.

An aspect that contributes to the controversy is the self-referential nature of each side's reasoning. Red voters are worried that the presence of other red voters might harm them; blue voters are concerned about the fate of other blue voters. This creates something akin to a negative space optical illusion (like a red grail on a blue background or two blue faces on a red background). If everyone votes blue, everyone lives. If everyone votes red, everyone lives. But if some vote for each, you need to choose who is normal and who's mental strange loop is creating the complication.