They don't assign colors based on wavelength, but on chemical composition. nitrogen (red), hydrogen (green), oxygen (blue), and helium (violet). (via Hubblesit

They don't assign colors based on wavelength, but on chemical composition. nitrogen (red), hydrogen (green), oxygen (blue), and helium (violet). (via Hubblesite)[http://www.hubblesite.org/newscenter/archive/releases/2000/07/image/a http://www.hubblesite.org/newscenter/archive/releases/2000/0...]