In Western cultures, some colors show not only the "color" but also another meaning such as fear, anger or sadness.
When people see the color "red", they think of anger, danger or caution. This is why many dangerous signs are red. The color "blue" sometimes means that someone is sad. "Blue" music is usually quite slow and sad.
Green is the color for jealous people. There is a saying "green with envy", which means that someone really wants to have something which belongs to another person.
Yellow is the color which shows fear. People who are not brave or are always afraid are called "yellow". Sometimes people call them "chicken". Chickens are yellow too, aren't they?
Even black and white have other meanings. White means "good" and "clean". A bride usually wears a white dress. But black often shows that something is bad or evil. I wonder why bridegrooms usually wear black?
