RED

Red is the colour at the end of the visible spectrum of light, next to orange and opposite violet. It has a dominant wavelength of approximately 625–740 nanometres. It is a primary colour in the RGB colour model and the CMYK colour model and is the complementary colour of cyan. Reds range from the brilliant yellow-tinged scarlet and vermillion to bluish-red crimson and vary in shade from the pale red pink to the dark red burgundy. The red sky at sunset results from Rayleigh scattering, while the red colour of the Grand Canyon and other geological features is caused by hematite or red ochre, both forms of iron oxide. Iron oxide also gives the red colour to the planet Mars. The red colour of blood comes from protein haemoglobin, while ripe strawberries, red apples and reddish autumn leaves are coloured by anthocyanins.

Red pigment made from ochre was one of the first colours used in prehistoric art. The Ancient Egyptians and Mayans coloured their faces red in ceremonies; Roman generals had their bodies coloured red to celebrate victories. It was also an important colour in China, where it was used to colour early pottery and later the gates and walls of palaces. In the Renaissance, the brilliant red costumes for the nobility and wealthy were dyed with kermes and cochineal. The 19th century brought the introduction of the first synthetic red dyes, which replaced the traditional dyes. Red also became the colour of revolution; Soviet Russia adopted a red flag following the Bolshevik Revolution in 1917, later followed by China, Vietnam, and other communist countries.

Since red is the colour of blood, it has historically been associated with sacrifice, danger and courage. Modern surveys in Europe and the United States show red is also the colour most commonly associated with heat, activity, passion, sexuality, anger, love and joy. In China, India and many other Asian countries it is the colour of symbolizing happiness and good fortune.