When we were little kids, we knew about traffic lights. The color red means stop, the color green means go. And the color yellow means slow down or tells that you have to be careful. But why are these colors used for traffic lights? Why couldn’t they be colors like blue, brown or orange? 【小题1】

Well, it’s important to know that before there were traffic lights for cars, there were traffic signals (信号) for trains. At first, railway companies (公司) used red to mean stop, white to mean go and green to tell people to be careful. 【小题2】 They could easily mistake stars at night for the signal to go. So railway companies made some changes. They used the color green to mean go, and the color yellow to ask people to be careful.

But believe it or not, yellow was also used to mean stop in the 1900s. 【小题3】 After more highly reflective materials (反光材料) were developed, people once again used red to mean stop. 【小题4】 And it is the color with the longest wavelength (波长), so people can see it from a faraway place than other colors. As a result, the color yellow is used to mean “be careful” because it has a little shorter wavelength than red, but not as short as green.

【小题5】 They do play a role in keeping the traffic in order every day.

Have you ever walked into a room and felt relaxed? It could be because the walls were painted blue, a calm and peaceful color.

【小题1】

Some colors can make us feel calm and peaceful. They are cold colors. Blue is one of these. Wearing blue clothes or sleeping in a blue room is good for our mind and body. 【小题2】 Blue is also the color of sadness, so you may say you’re feeling blue when you are feeling sad. White is another calm color. You should wear white clothes if you are feeling nervous. White is also the color of purity (纯洁). Many women like to be in white on their wedding day. Green is the color of nature. 【小题3】

Some colors can make you feel warm. 【小题4】 In cold places, people use warm colors like orange and yellow instead of white and blue in their homes. Orange shows joy. It can bring you success and cheer you up when you are feeling sad. Yellow is the color of the sun, so it can remind you of a warm, sunny day. Yellow is also the color of wisdom (智慧). 【小题5】 For example, they may use yellow school things. Red is one of the strong colors. Wearing red often makes us active.

In short, we can try out different colors if we aren’t feeling our best.