ROYGBIV

ROYGBIV is an acronym for the sequence of hues commonly described as making up a rainbow: red, orange, yellow, green, blue, indigo, and violet.

There are several mnemonics that can be used for remembering this color sequence, such as the name "Roy G. Biv" or sentences such as "Richard of York Gave Battle in Vain".

[1] Originally he used only five colors, but later he added orange and indigo to match the number of musical notes in the major scale.

[4] Isaac Newton's color sequence (red, orange, yellow, green, blue, indigo, violet) is kept alive today by several popular mnemonics.

[6] Another traditional mnemonic device has been to turn the initial letters of the seven spectral colors into a sentence, most commonly "Richard Of York Gave Battle In Vain"[7] (or the slight alternative "Richard Of York Gained Battles In Vain").

The conventional gradient colors of the rainbow symbol
Newton's color wheel that introduced indigo as a basic color. The uneven color division along the color circle correlates with the intervals of the musical major scale . Illustration from Newton's Opticks , Fourth Edition, 1730.