KnowYourPhrase.com - Meanings and Origins of Phrases

Losing money. Being in debt.
Note: The origins for most phrases and sayings cannot be said with a certainty. What's provided are theories that may be plausible to how a phrase originated, but not necessarily so. 

In addition, quotes that contain a particular phrase may be taken from old newspapers, poems, or books that were written centuries ago, but this by no means confirms that the phrase originates from said newspapers, poems, or books. In all likelihood, if an expression is being used in a newspaper, it's probably already a well known saying and is from an older time.
* James created a furniture company knowing ahead of time that he'd be working in the red, but he hopes business will pick up in the following months so he can start turning a profit.
Know Your Phrase - The Origins And Meanings For Idioms And Phrases  |  I-Letter Sayings
It's believed that this phrase originates from the practice of using red ink to signify a financial loss.
Thus, a business that is "in the red," is a company that is losing money.

It's possible that this phrase originates sometime during the early 1900s, as there are numerous 
newspapers from that period of time that 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:

    "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."

A list of phrases starting with the letter I.
Phrases and Idioms
The meaning of the phrase 'in the red.'
Origins:
Examples