The Dawn spacecraft is on its way to Ceres, and has started sending back new images of the dwarf planet.
Shattering Theory
All large asteroids have been bombarded over the ages, and as a result smaller chunks have been cast adrift in the solar system. Some of these smaller bits fall to Earth as meteorites. One of the things we notice about meteorites is that many of them have certain similarities of composition and chemical signature. As a result they can be identified into groups. This would imply that these groups have a common origin, likely a particular asteroid.
Color Kin
We generally think of asteroids as looking like gray rocks. While that’s true to our limited eyes, more sensitive instruments find they have a variety of colors. You can see an example of this in the image above of the asteroid Vesta. This false color image was made by observing Vesta at various wavelengths in the visible and infrared spectrum. It shows that Vesta has variations in color too subtle for us to see with our eyes.