How to match the red short hat sweater?

Matching principle: colors must be harmonious and not too different. If there must be a big difference, there must be embellishment, such as: white shirt with dark tie, or white pattern on tie, or white shirt with dark pattern, so as to achieve overall unity, small changes, not rigid, not fancy. As long as you grasp the principle, how to do it depends on your own preferences. I hope you are satisfied.