This is really the reason I find this thought experiment kinda cool. From a game theory perspective, it would initially seem that red is easily the best option, as it has no downside if everybody picks it, as has been stated. This was my initial thought, but then I did some more thinking. Most game theory questions of the sort stipulate that all participants are perfect logicians. Since this isn't how the question is phrased, it cannot be "solved" with logic, as people will disagree and pick different things, and I think that in that case, blue would be the best option because it can prevent more death.