If I can only have three crayons, I want red, green and blue. By layering the colors over each other I can create a wide variety of colors.
It’s basic color theory folks, not rocket science.
The word red comes from the Old English rēad. Further back, the word can be traced to the Proto-Germanic rauthaz and the Proto-Indo European root reudh-. In Sanskrit, the word rudhira means red or blood.
The word green is closely related to the Old English verb growan, “to grow”
The word itself is derived from the Old French word bleu.