Green is an important color in our life. But "green" is more than just a color. It is the color of grass and leaves. It is also the color of most growing plants. Sometimes, the word"green"means young and growing. It is something that is not ripe (成熟). If a cow has no horn (角), it is green. If you come to a new job, you are a green hand, too. Green is also the word to say one's feeling. You are always good at English, but your friend David is not. If David is not happy with you, maybe just because he can't be as good as you(和你一样好). Then he is green. Green has another wonderful meaning. If you often take a bus to go out, not a car, we say you are going green. Because you love the world in a better way.