Many daily American expressions are based (......) on colours. Red is a hot colour. Americans often use it to represent heat. When they say "red-hot", that means they are very angry about something. Loud music is popular with many people. Some may say that such music is red-hot. Pink is a lighter kind of red. People sometimes say "I'm in the pink" when they are in good health. The expression was first used in America at the beginning of the 20th century. It probably comes from the fact that many babies are born with a nice pink colour that shows that they are in good health. Blue is a cool colour. The old Blues music in the United States is the opposite of red-hot music. Blues is slow and sad. Someone who is "blue" is very sad. The colour green is natural for trees and grass. But it is an unnatural colour for humans. A person who has an upset stomach may say "I'm feeling a bit green". A person on a boat who is feeling very sick from high waves can be said "look very green". Sometimes a person may be very jealous because he does not have anything as nice as someone has, like a fast new car. That person may say "I'm green with envy". Some people are green with envy because someone has more dollars or "greenbacks". Dollars are called greenbacks in American slangs because that is the colour of the bottom of their bank notes. The colour black is used often in expressions. People may say "it's a black day" when everything goes wrong on that day. In some cases, colours describe a situation. _ were common during the World War II. All the lights in a city were turned off at night to make it difficult for enemy planes to find their aims in the dark. We describe a day on which everything goes wrong as   _  .
a red day a green day a pink day a black day