Galaxies who are redder have high values from the measurement of the mass of the bulge (concentration of stars), and central black hole; determining its color. The mass in the central bulge is the key to knowing the color of the whole galaxy. Almost most galaxies have supermassive black holes in their centers. If the black hole is more massive, and the more energy it releases into the galaxy in form of powerful jets, and x-ray emission. It can blow away, and heat up gas, to stop new stars from forming.