I learned this today, and it kind of blew my mind. We know a rainbow has seven colors, from red to violet (ROY G BIV). Violet is a true color. But purple isn’t! Purple is a mix between blue and red. When it comes to what our eyes see as different colors, it’s all about the wavelength of light. Red has a long wavelength. Blue is short. And purple combines the two. It’s the ONLY color that combines two completely different wavelengths of light. In terms of true colors (based on wavelength), purple doesn’t exist anywhere–except in your brain.
Did you know? Some scientists think the purple pigment found in some plants’ leaves acts as a sunscreen to protect them from too much light. source
Want to know more? Check out this deep dive into the color purple here.