Blue

Blue is one of the colors of the rainbow that people can see. It is one of the primary colors (colors that can be mixed with other colors) of light, along with red and green. Apart from indigo and violet, it has the shortest wavelength of colors in the rainbow (about 470 nanometers).

Blue paint can be made by mixing magenta and cyan paint.

Blue is the color of the Earth's sky and sea. Earth looks blue when seen from outer space by astronauts.

It is the color of cold, introversion and openness, by opposition to the red, which is the color of warm, extroversion and the closure. In alchemy, blue is also the color of the warm introvert (blue fire), by opposition to the red, which is the color of the warm extrovert (red fire).

Blue is usually associated with masculinity, harmony, conservatism, liberalism, the cold, sadness, calmness and royalty.