There are many coloring options that a contractor may apply:

Integral coloring is mixed into the material. This is good for earth tones and pastels.
Dry-shake color hardeners are laid on the surface of the concrete, and provide a more intense color palette, and improve the strength and density.
Surface-applied color are dyes, stains, and tinted release agents that can be used in conjunction with the first two options that help make textures look more like the natural materials they resemble.