八光流柔術 and traditionnal light spectrum vision


On the Hakkoryu Jujutsu website we can read

> The name “Hakkoryu” is based on a philosophical Japanese view of the color
> spectrum as being divided into nine bands of light. The eighth shade is
> infrared, which is invisible to the naked eye but extremely powerful, both
> characteristics apparent in Hakkoryu’s techniques.

But I don't find anything on that subject. I'd like to read more about this
philosophical Japanese view. Any clue ? Sorry if that's the wrong place to
ask.

