
Black sheep (of the family) - a person who has done something bad that brings embarrassment or shame to his or her family
Example: She never went to college, she’s the black sheep of the family
Catch someone red-handed - discover someone while they are doing something bad or illegal
Example: He was caught red-handed while trying to steal a car

Get the green light - get permission for something to happen
Example: I got the green light from my boss to begin the project.
The grass is greener on the other side - people think they would happier if thing were in different
Example: I sometimes think I'd be happier teaching in Spain. Oh well, the grass is always greener on the other side!

Green with my envy - jealous
Example: She was green with my envy when she saw my new car.
Once in a blue moon - rarely
Example: We go out once in a blue moon

In black and white - in writing
Example: It was in the agreement, in black and white
Roll out the red carpet - greet someone hospitably
Example: They rolled out the red carpet for me

A white lie - a small, harmless lie
Example: I told a white lie not to hurt her feeling
Out of the blue - suddenly
Example: He got mad at me out of the blue
Y Vân (theo Ella Language)