Red

Red is the color that is on the outside edge of the rainbow. It is one of the three primary colors, along with blue and yellow. Red light has a wavelength between 630-750 nanometers.

Use by political movements
As early as the 9th century, the Khurramites successors to the Mazdak religion and proto-communists in the Middle Ages of the Middle East used red as their symbol for revolution. Even before Europe's Revolutions of 1848, Socialist red was used as a color of European Revolutionaries, often in the form of the red flag. It was also used by Garibaldi's camicie rosse (redshirts) in the Italian Risorgimento, and taken up by Leftist and generally revolutionary groups, while the white of legitimist Bourbon partisans became associated with pre-World War I conservatives. This relates to the term "Blood of the workers", representing the suffering of the proletariat. For instance the Civil War in Russia and the Civil War in Finland were fought between the Red Army and various White Armies.

The identification of Communism with Socialist red (with the red flag being the primary color of the flag of the Soviet Union) and the red star being a Communist emblem led to such Cold War phrases as "the Red Menace" and "Red China" (distinguished from Nationalist China, "Blue China"). China's de-facto anthem under Mao Zedong was "The East Is Red". Mao Zedong was sometimes referred to as a "red sun". The color was also associated with political vehicles such as the Red Guard in China and the Red Guards during the Russian Revolution of 1917 as well as with left wing paramilitary groups such as the Red Army Faction in Germany and the Japanese Red Army. Red remains associated with parties on the left of the political spectrum.

Social-democratic political parties throughout the world, particularly in Europe, are most commonly symbolised by the colour red.

In the United States, red is associated with the right-wing Republican Party and blue with the Democrats – a reverse of the traditional European scheme. This convention is relatively recent: before the 2000 presidential election, media outlets assigned red and blue (the colors of the American flag) to both parties, sometimes alternating each election. The fixed usage became established in during the 39-day recount following the 2000 election, when coverage began discussing the contest in terms of "red states" versus "blue states".