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.
Galaxies generally don t escape collision.
To illustrate the comparative distances of stars vs. galaxies, if stars were the size of a quarter, the next star would be 400 miles away. When spiral galaxies collide, because of gas and dust, new stars are formed. The Ring galaxy is a half of a billion light years away. It is exotic. The Cartwheel galaxy used to be like the Milky Way, but an intruding galaxy caused a compression wave.