You vote for the yellow by not letting red think they have a chance of winning, making room for a candidate better than blue in the future elections. Democracy is an ongoing effort, not a magic thing that happens on election day.
Then you're not doing enough political activism to make people confident that their vote matters, and that a vote for blue is the only effective way to vote for Ranked Choice voting, which is in turn the only way of giving anyone other than red or blue a real chance in the future.
Or... And hear me out here: Biden, the president of the United States, is more responsible than I am for his chances in the general election. I know that's a hot take for some of you.