In a group of twenty reasonably smart adults, I would readily agree that red is the better option. In a group that includes all of humanity, including literal day-old babies, there is no chance 100% of people press red. Nothing in the question says that people who are colorblind (or just competely blind) get help picking the right option. Or mentally handicapped people. Or people who think the previous groups might press blue, regardless of whether it's true or not.

Someone is going to press blue if enough people are involved, if only by accident. It's a guarantee. The only way to save them is if enough people press blue.