Red is a primary colour that matches the longest wavelength of light that can be seen by people at 625–740 nanometres. Red is the recognised color of the sun, fire and blood. It is deemed a bold, brave, powerful and hot color. Red is generally used to make a dramatic declaration and is a traditional national and political colour. Sunlight is white, meaning it is made up of each wavelength of light.
When sunlight hits particles of air in the air, shorter wavelengths of light are scattered more easily than the large wavelengths of red. This is the reason that sunlight looks to be red. This effect is especially strong when the sun is low on the horizon at sunrise and sunset so that the whole sky can glow red.