In surveys made in Europe and the United States, green is the color most commonly associated with nature, life, health, youth, spring, hope and envy. In Europe and the U.S. green is sometimes associated with death (green has several seemingly contrary associations), sickness, or the devil, but in China its associations are very positive, as the symbol of fertility and happiness. In the Middle Ages and Renaissance, when the color of clothing showed the owner's social status, green was worn by merchants, bankers and the gentry, while red was the color of the nobility. The Mona Lisa by Leonardo da Vinci wears green, showing she is not from a noble family; the benches in the British House of Commons are green, while those in the House of Lords are red. Green is also the traditional color of safety and permission; a green light means go ahead, a green card permits permanent residence in the United States. It is the most important color in Islam. It was the color of the banner of Muhammad, and is found in the flags of nearly all Islamic countries, and represents the lush vegetation of Paradise. It is also often associated with the culture of Gaelic Ireland, and is a color of the flag of Ireland. Because of its association with nature, it is the color of the environmental movement. Political groups advocating environmental protection and social justice describe themselves as part of the Green movement, some naming themselves Green parties. This has led to similar campaigns in advertising, as companies have sold green, or environmentally friendly, products.

Answer this question, if possible (if impossible, reply "unanswerable"): What does a red light indicate?
unanswerable