How come there's no all 7 colours of the actual قوس قزح on a LGBT قوس قزح Flag instead of only 6? I'm just curious that's all. Does anyone know for sure the right answer to this simple سوال of mine?

What ever happened to the last colour, colour indigo? It supposed to be the colour of the last stripe on a قوس قزح Flag. Where did it go & how come the 7th colour of a real قوس قزح somehow has managed to get lost since it was created back in 1978?