1
general::
Phrase(s): *in the red
Fig. losing money. (*Typically: be ~; go [into] ~; as opposed to in the black.) • State government has been operating in the red for five straight years. • What with all those car repairs, we’re going to be in the red this month.
McGrawhill's American Idioms And Phrasal Verbs
2
general::
In debt, as in Joshua can't keep track of funds, so half the time his company is in the red. This expression alludes to the book-keeping practice of marking debits in red ink and credits in black. It survives even in the age of computerized accounts. So does the antonym, in the black, for being financially solvent or out of debt, as in Bill was happy to say they were in the black. [Early 1900s]
American Heritage Idioms