Blue

Blue is the name of a colour, a pigment or a light. It is one of the seven coulours of the rainbow between indigo and green. In the spectrum the lights refract according to their wavelengths. From highest to lowest wavelength are the red, orange, yellow, green, blue, indigo, and violet lights respectively, and thus red bending the least and violet bending the most. When blue light is reflected from an object we see the object in blue colour.

Informally, feeling blue denotes the melancholy, depressed, or sad mood of a person. Pornographic contents are also called blue, such as blue movies. A language is also said to be blue if it is blasphemous, cursing, or swearing. The term is also used for anything blue, such as the sky, sea, etc.