Blue in the face
Do something till you are blue in the face.
You can walk around till you are blue in the face, but you won&`&t find a shop selling shoes as cheap as these!
Mom told Alex to do his homework until she is blue in the face, but Alex didn&`&t do it.
once in a blue moon
A: "Do you ever eat pork?”
B: “Once in a blue moon; I prefer beef.”
out of the blue=suddenly
He divorced out of the blue.
a blue joke下流的笑话
a blue movie/film 色情电影