Random Questions; Random Days... Thursday, June 26

Name some colors that clash. Why might a person use these colors together?

I've never cared for orange and blue together. Red and yellow is another combo I really don't like. It reminds me too much of mustard and catsup! wow!!!
I think someone might use these colors together to make a point. I think I even used blue and orange together in my photo albums once. It seemed to work! Maybe it draws attention to certain things.