There aren't any idioms that mean "black" that I know of. There are plenty of similes, like "black as the ace of spades."
It depends on how you use it. If you mean literal colors, then it's not an idiom. If you say something like "It's all there in black and white," then it's an idiom meaning that something is printed.
black sheep
This is not an idiom. It is comparing one thing to another, so it is a simile. Remember: "AS ___ AS___" means A Simile! It is just saying that something is very black.
siah o sufaid
It means to be very angry.
She sees every situation in black and white although she knows it is wrong.
"A black day" is an idiom in contemporary English that is relatively uncommon but still quite useful. With "black" referring primarily to darkness (of night, of a storm, etc.) when there ought to be light, its basic meaning is simply this: "a bad or difficult day."
African American, also known as Black English or Black Idiom
In debt. Its antithesis, "in the black," refers to having a balanced budget.
Criticism from someone who is just as bad.
Meaning a very obvious difference between 2 things.
Pitch, as known in the context of the idiom "pitch dark" or "pitch black", is also called bitumen or tar pitch. It is a nearly-solid, very black ooze that comes from petroleum (which in its raw form is also very black).The idiom "pitch black" is a minor rearrangement of the simile "black as pitch" which based on the above definition becomes self-descriptive: very, very black.