Wiktionary
scream blue murder
vb. (context idiomatic English) To protest loudly or angrily.
Usage examples of "scream blue murder".
If it does, you have my permission to wallop me and scream blue murder.
Sir Giles would scream blue murder but there was nothing he could do.
They would scream blue murder at first, but when they realized there was nothing they could do about it, they would soon settle down and be grateful for small mercies.
If this fellow's boss stands by him and they both scream blue murder, he might get away with it.