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

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