Losing money. Being in debt.
it's believed this phrase originates from accountants who are selective on which color ink they use when making entries in a firm's book.
If someone is doing business at a loss, instead of using black ink, accountants will use red to write down the deficit.
Indeed, the color red is prominently used in businesses to signify a loss, while black is used to indicate a profit.
Thus, a company that's interested in making money would desire to be 'in the black' rather than be 'in the red.'
因此，想赚钱的公司都很希望自己是in the black而不是in the red.
This idiom seemingly originates from the early 1900s.
There are numerous newspapers from that period of time which use the phrase when referring to businesses functioning at a loss.
For example, the Daily Globe from 1927, under the subheading 'Failed to get Interest,' reads:
比如，Daily Globe在1972年的副标题为Failed to get Interest的文章中这么写道：
"I regret to report to you that the people who put money into it failed by $30,000 to earn even operating expense and depreciation. The company is in the red all the time."
1.His company, however, ended up in the red. It lost more money than it earned. The company was no longer profitable.
2.Work out how much sleep you owe your body and find out how to recover if your sleep account is in the red.