Why are primary colours called primary?

A primary color is one of three, basic colors, used to produce all other colors and shades, without these colors no other colors could be made. The three primary colors are Red, Blue and Yellow, no other colours can be mixed to make Red, Blue or Yellow, while Yellow + Red = Orange, as Blue + Yellow = Green and Blue + Red = Purple. White is a perfect mixture of all three colors and Black is a "Shade" of any of them. Thanks for listening. I love you all, goodbye.