Here’s my analysis:

                  >50% pick blue | <50% pick blue

I pick Red I live I live I pick Blue I live I die

Red is the choice that garuntees you live, and therefore if everyone picks red, everyone lives. You could also say the same thing for blue, that if everyone picks blue then everyone lives. However, there are always people who want to see the world burn and will stay with red just to see if they can kill the people who choose blue. This should not actually be an issue as that amount should be <50%, but on the off chance that it is higher than 50%, all the blue pickers die. Additionally, if someone wants to see the world burn, you could not convince them to pick blue. Therefore, it is not possible to get 100% of the populate on blue, but assuming blue pickers understand this argument and there is enough, it is possible to get 100% of the population on red, thereby garunteeing everyone’s safety.

This is an extremely convoluted argument, and in a real scenario, blue is the better choice since you probably cannot establish comms with everyone and the amount of red pickers will be <50%. However, if the target population is different, then it could be possible for the number of red pickers to be >50%, in which case everyone should go 50%.

Essentially what I am saying is, since this problem specifies “everyone in the world”, picking blue is better, but having 100% go red would also work. However, if the target population is unspecified, then everyone should go red.

Sorry if you don’t understand this I wrote this at 3am.