口语对话：
 
Roger: there are several colors of traffic lights?
罗杰：交通灯都有几个颜色？
Alice: three, respectively, red, yellow, green.
爱丽丝：三个，分别是红色、黄色、绿色。
Roger: what does it mean to be red?
罗杰：红色是什么意思？
Alice: red means no traffic.
爱丽丝：红色表示禁止通行。
Roger: what about the green one?
罗杰：那绿色呢？
Alice: green means that you can pass.
爱丽丝：绿色表示可以通行。
Roger: that yellow one?
罗杰：那黄色呢？
Alice: yellow is a reminder, when the red and green conversion.
爱丽丝：黄色是提醒，在红色与绿色转换的时候。
Roger: why do you want to use these three kinds of colors?
罗杰：为什么要用这三种颜色啊？
Alice: because these three colors are more eye-catching, even if it is rainy or foggy days, crash can also be seen.
爱丽丝：因为这三种颜色比较醒目，就算是雨天或者雾天，死机也可以看到。
Roger: Oh, I understand!
罗杰：哦，我懂了！