Blue – Simple English Wikipedia, the free encyclopedia

Blue is one of the colors of the rainbow that people can see. It is one of the seven colors of the rainbow along with red, orange, yellow, green, indigo and violet.Apart from indigo and violet, it has the shortest wavelength of these colors (about 470 nanometers).. Blue is the color of the Earth’s sky and sea. Earth looks blue when seen from outer space by astronauts.

https://simple.wikipedia.org/wiki/Blue