Rainbows are optical and meteorological phenomena that reason of a spectrum of light to appear in the sky when the Sun shines onto droplets of moisture in the Earth's atmosphere. They take the form of a multicolored arc, with red on the external part of the arch and violet on the inner section of the arch. More rarely, a secondary rainbow is seen, which is a second, fainter arc, outside the primary arc, with colours in the differing order, that is, with violet on the outside and red on the inside.
A rainbow spans a permanent spectrum of colours. Traditionally, however, the chain of colours is quantized. The majority cited and remembered sequence, in English, is Newton's sevenfold red, orange, yellow, green, blue, indigo and violet. "Roy G. Biv" and "Richard of York Gave Battle In Vain" are admired mnemonics.
Though rainbows are bow-shaped in most cases, there are also phenomena of rainbow-colored flooring in the sky: in the shape of stripes, circles, or even flames