i am a certified ussf referee; you have to take a weekend course and a test at the end to be certified. As stated above, it is the color of the patch that determines your level. They tell us to get at least 3 shirts so you don't blend with teams and also for weather purposes. Referee is a subjective job-not all people referee the same way..as i have witnessed in club games to college games to youth games to high school games. The color shirt has nothing to do with anything...LOL