What is the origin of the idiom "in the black" and when to use it?

The idiom "in the black" originated in the world of finance and accounting, where it is used to describe a business or organization that is profitable and has positive net income. The idiom is commonly used to describe a range of scenarios, such as when a company's profits exceed its expenses, when an individual's savings exceed their debts, or when a non-profit organization has enough funds to cover its expenses and operations.