How many colors are there in a rainbow?

The story behind the answer

Seven colors are traditionally recognized in a rainbow: red, orange, yellow, green, blue, indigo, violet (ROYGBIV). A rainbow forms when sunlight enters raindrops, is refracted, internally reflected, and dispersed, spreading white light into its component wavelengths. Each color emerges at a slightly different angle, so we see a fanned-out arc with red on the outer edge and violet inside.

Fun fact: the spectrum is actually continuous, not made of strict bands. Isaac Newton popularized the seven-color division in the 17th century, partly to align with the seven musical notes and classical “planets.” To remember the order, use the mnemonic ROYGBIV or “Richard Of York Gave Battle In V