"to be green" is to be new at something, inexperienced, a rookie or novice
It's not an idiom. It's American slang for money, because American paper bills are green (and they fold when you put them in your pocket).
It means swearing violently and creatively.
It means the person looks sick. Usually they are pale and green in the face.
It means someone who is very good at things like gardening and growing things.
Having a green thumb. (Being successful with plants and ACTUALLY planting the plants.)
It's not really an idiom. It means "what are you thinking about."
RFP is not an idiom. It's an abbreviation.
It is not an idiom, it means your nose is itching.
It's not an idiom. It means the tip of your nostril.
idiom means expression like a page in a book
"Sieve" is not an idiom. See the related link.
The green light on a traffic light means to go ahead. If you "get the green light," you have permission to move ahead on whatever project you are dealing with.