[green] Green is the general term for colors that fall between yellow and blue in the color spectrum. Emerald (bright), forest, and army (dark grayish) are common modifiers that describe shades of green.

Idioms:

green
inexperienced. ‘Frank’s replacement is so green I’d be surprised if she’s ever worked a day in her life.’

green light (something)
to provide authorization. ‘The committee finally gave me the green light to fire you.’

green with envy
very envious. ‘Yes, I’m dating John, and I see you’re green with envy, but don’t worry, there are other guys for you.’