ˌblack and ˈblue adjective
skin that is black and blue has bruises (=dark marks) on it as a result of being hit:
If you do that again, I’ll beat you black and blue.

[TahlilGaran] Dictionary of Contemporary English ▲

black and blue
if a person or part of their body is black and blue, their skin is covered with bruises (= black marks caused by being hit).
He was beaten black and blue at boarding school.

[TahlilGaran] English Idioms Dictionary ▲

black and blue
bruised
My shoulder was black and blue after I fell down the stairs.

[TahlilGaran] English Idioms Dictionary ▲

black and blue
adj. Badly bruised.
Poor Jim was black and blue after he fell off the apple tree.

[TahlilGaran] English Idioms Dictionary ▲