The color purple does not exist in nature. It is a creation of our minds.
On the light spectrum, there is no color purple between red and blue. There is no color purple in a rainbow. The color between red and blue is green.
When red light and blue light enter our eyes we’re supposed to see green. But our mind says, “that’s not green,” because our green receptor isn’t firing. So it invents purple.
Because there is not a frequency that corresponds to purple, I suppose that my purple may be just a little bit different from your purple, because each of us create it.
Here’s a great explanation:
Fanatic Cook 