be in the red
If you or your bank account are in the red, you owe money to the bank
see red to become very angry
once in a blue moon not very often
My sister lives in Alaska, so I only see her once in a blue moon.
using the imagination to think of ideas that do not yet have practical uses or make money: Blue-sky thinking involves a group of people looking at an opportunity with fresh eyes.
out of the blue
If something happens out of the blue, it is completely unexpected:
One day, out of the blue, she announced that she was leaving.
be green with envy
to be very unhappy because someone has something that you want:
Chad is heading off to Spain for the week, and I'm green with envy.
green fingers (UK) / green thumb (US) the ability to make plants grow
For more idioms follow A Cup of English on Facebook.
once in a blue moon