From space, our earth looks like a blue planet. Blue is the colour of the sky and sea, of distance. It evokes feelings of freedom and optimism.
At the same time, we may feel blue, sing the blues or have the blues; this shows how blue also carries a flavour of sadness.
People of aristocratic or royal lineage are said to have blue blood, and top quality items are classified with the blue ribbon designation.
Blue has also some religious associations: it is associated with the Virgin Mary in Catholic art, is seen as emblematic of God the Father in Judaism, and is often used to decorate mosques, like the Blue Mosque in Istanbul, a symbol of Islam.
Blue is the colour of a few rare foods, like blueberries, which are healthy and nutritious and contain antioxidant chemicals that are said by some to support memory and learning.
Blue is the colour of the throat chakra, and represents our energy of expression and communication. Any shade of blue is soothing and relaxing when used for clothing and decor. Indeed, more blue clothing is worn than any other colour, especially by men. Many uniforms for military and airline personnel are blue. Blue cars are also very popular.
Blue is also the colour of the ancient stone lapis lazuli, which is used as a gem and also ground to use as dye. This ultramarine dye has been in use since ancient times, and can be found on the blue and gold death mask of Egypt's ancient Pharaoh Tutankhamen, or King Tut.