Using idioms make you sound more advanced and there are tons of them. But today I chose only five idioms related to colours.

(I used Cambridge dictionary)

1. Out of the blue

If something happens out of the blue, it is completely unexpected.

Sentences:

* One day, out of the blue, she announced that she was leaving.

* My old roommate called me out of the blue.

2. Green with envy

to be very unhappy because someone has something that you want.

Sentences:

* Chad is heading off to Spain for the week, and I’m green with envy.

* Ireland’s economy turned the world green with envy. ~Times, Sunday Times (2009)

3. Gray area

a situation that is not clear or where the rules are not known.

Sentences:

* The difference between gross negligence and recklessness is a legal grey area.

* There is a large grey area where we don’t know what to say.

4. Catch someone red-handed

to discover someone while they are doing something bad or illegal.

Sentence:

* He was caught red-handed taking money from the till.

5. tickled pink (informal)

it means to be very pleased.

Sentence:

* I was tickled pink to be invited.

And here is a link for their (flashcards)

All the best 😉