Blue is one of the three primary pigments, along with red and yellow, and one of the three main colors of light along with red and green. With pigments, such as with paint, blue is combined with yellow to make green, or with red to make purple.
In US politics, blue is the color of the Democrats starting with the 2000s. It is sometimes associate with wealth, such as in the terms blue blood and blue chip. Elsewhere in the world the color blue represents conservatism. Blue was also used for the colors of the French Revolutionary radicals, and to a lesser extent the Blue Ants of Mao Zedong in Communist China.
The color blue corresponds to wavelengths of 435 nanometers to 500 nanometers in the electromagnetic spectrum.<ref>http://hyperphysics.phy-astr.gsu.edu/hbase/vision/specol.html#c1</ref>