From: http://www.bbc.co.uk/worldservice/learningenglish/language/2014/03/140320_todays_phrase_in_the_red.shtml

In the red

The Welsh Guards on parade
The Welsh Guards, in their red uniforms, practice for the Trooping the Colour ceremony in London

Today's Phrase

If you owe money to a bank, you are in the red. Also, if a person or a business is in the red, it means they are losing money.
Examples:
Because the airline had to give everyone their money back after the delays, they now say they're operating in the red.
I've paid off most of my credit card bills - but I'm still in the red.

Take note

If someone is in the pink, they are in good health.
Example:
Ruth looks very well - she's certainly in the pink.

Interesting fact

The soldiers shown in the photo are from the Welsh Guards. Together with other regiments of the British armies, they perform a ceremony called Trooping the Colour in June every year to mark the official birthday of Queen Elizabeth II.