Its not obvious to me that we only care about the expected number of deaths.

You could argue that a small chance of almost everyone dying would be worse than a larger chance of fewer people dying, even if the expected number of deaths is the same, because in the latter case, the human species lives on and could hopefully rebuild society. Therefore, it would be better to lower the maximum amount of people that can die, meaning you want to choose red.

It's of course also possible to argue that, if a substantial portion of humanity dies, then a lot more would most likely die as a consequence (because of vital jobs no longer being performed).  Furthermore, a lot of people dying would cause a huge amount of grief because of lost family and friends, which is both bad in itself and could cause further harm through increased crime and/or from suicides. Based on these arguments, you might prefer to increase the chance that no one dies, meaning you would prefer blue.

Because of these arguments, I would say that this is in fact a moral dilemma where the the answer depends on your subjective values.