COLOR Something that is ~ is the color of the sky on a sunny day. ADJ If you are feeling ~, you are feeling sad or depressed, often when there is no particular reason. Why so blue? PHRASE once in a blue moon千载难逢，难得一次 To do something “once in a blue moon” is to do it very rarely: “That company puts on a good performance only once in a blue moon.” The phrase refers to the appearance of a second full moon within a calendar month, which actually happens about every thirty-two months. You should be grateful for the extra job offer. Things like that come along only once in a blue moon. PHRASE blue blood 西方国家常用 “蓝血” 来形容欧洲贵族。这个说法源自西班牙王室。古老的西班牙人认为贵族身上流淌着蓝色的血液，因为那时候，古老的卡斯蒂利亚贵族宣称自己的血统最为高贵、纯正。贵族常自豪地展示自己雪白小臂上清晰可见的蓝色静脉血管，称之为蓝血。所以，现在英语里表示“出生贵族，出生高贵” 的意思 Crown Cadillac symbolizes the family’s coat of arms, pearl crown on the 7 metaphor for the royal blue blood. He boasted a lineage of pure blue blood.
cold blood 就是“冷血；故意” 还有“蓄意和预谋杀人”的意思。The question here is did this man kill a fellow human being in cold blood! 这里的关键是，究竟这个人有没有残忍地杀害了另外一个人。
bad blood 这次不是“坏掉的血”了。真正意思是“恶感”、“敌意”、“仇恨”。 There’s too much bad blood between them. 他们之间有很深的敌意。 Blood is thicker than water “血浓于水” They say that blood is thicker than water, that our relatives are more important to us than others. 人们说血浓于水，即我们的亲属比别人对我们更重要。
get sb.’s blood up这可不是说“令某人热血沸腾了”，而是“使震怒、生气”的意思。 His behavior really got his father’s blood up. 他的行为真的让他父亲很是震怒。
瘀青的；发紫的 There is a tube of blue. 这儿有一管蓝颜料。
blue Monday忧郁的星期一(尤指与欢乐的周末对比) blue-pencil 编辑；修订；删除 blue-eyed boys宠儿 blue-sky 无价值的, 不切实际的 blue sky bargaining漫天讨价 blue fear极度的惊恐 drink till all’s blue一醉方休 out of the blue完全出于意外 a bolt from the blue晴天霹雳 a blue joke下流的笑话 (记住，不是yellow哦) blue stocking女学者 blue ribbon蓝绶带；最高的荣誉；一流的
out of blue 出乎意料