The Flag of the Perseus Arm of the Milky Way Galaxy is composed of three colours - white, black and indigo.
The Milky Way is essentially composed of four major spiral arms, like a human body. Just as the magnificence of the universe unfolds in our cells, our Galaxy is like essentially a gigantic cell. But instead of endoplasmic reticulum, the super structure of our outer layer of cosmic 'body' on a galactic level is composed of Galactic Arms.
As each galaxy is a 'cell' of its own, it no accident that a cluster map of galaxies looks remarkably like in the internal architecture of cellular mind.