In the red

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 bookkeeping 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]