once in a blue moon 百年一遇（很少发生）
He passes his exams once in a blue moon!
他很少通过他的考试！
I cook once in a blue moon!
我很少做饭！

This movie always makes me blue!
这个电影总是让我感到悲伤！

That blue language is not welcomed here！
在这里，我们不欢迎大家说脏话！

I am kinda blue, can you help me take me home!
我有点儿喝醉了，可以来接我回家吗！

Black and blue 青一块紫一块

She is feeling surprised after hearing that news out of the blue!
她突然间听到这个消息，十分的惊讶！

She has some true-blue friends, I am jealous!
她有一些真朋友，我好嫉妒啊！

This is like choosing from between the devil and the deep blue sea!
这个选择让我进退两难！