Is Indigo a Real Rainbow Color? Fact-Checking Isaac Newton's Spectrum

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Q1: How many colors are actually in a rainbow?
Physically, a rainbow contains an infinite continuum of individual wavelengths ranging from roughly 380 to 740 nanometers. Neurologically, a typical human observer with normal trichromatic vision distinguishes roughly 100 to 150 distinct hues across that span, though cultural conventions collapse those subtle gradations into six primary categories: red, orange, yellow, green, blue, and violet.

Q2: Why do school systems still teach ROYGBIV?
Educational institutions prioritize standardized mnemonics over physical precision. Newton's seven-color spectrum became entrenched in textbooks throughout the eighteenth and nineteenth centuries. ROYGBIV remains popular because it is easy to memorize, even though modern science classifies the visible spectrum as a continuous gradient.

Q3: Is indigo an official color in modern digital color spaces?
In digital colorimetry (such as sRGB or Display P3), there is no dedicated indigo channel. Digital displays synthesize all colors using combinations of red, green, and blue (RGB) sub-pixels. CSS and web standards designate a specific hex code for "indigo" (#4B0082), but this is a specific software definition rather than a distinct spectral primary.