The uniform colors convinced them that the steady state theory was incorrect. The Big Bang theory can explain why this is the case. Our galaxy is a spiral galaxy. Spirals still give birth to new stars. M33 is an example of a spiral galaxy.
Young stars are blue.
Spiral galaxies appear blue due to the large number of young stars. They also rotate, whereas elliptical galaxies do not. In giant ellipticals, stars dive into the center and out. Some traumatic event had disordered their orbits. Elliptical galaxies form when two spiral galaxies collide.