All of the color composites except Pan were produced by Gordan Ugarkovic. Some original color composites were approximate true color (RGB) and some enhanced color (IRGUV). Emily Lakdawalla adjusted their color to make the moons appear similar in color and brightness. Mimas was left more gray (less red) than the smaller moons, which is true to life, but the relative color and brightness differences among the different moons are not intended to be precise representations of reality. The image of Pan (the highest-resolution available) was a monochrome observation, and has been colorized to roughly match the appearance of the others.
Images were selected for their resolution and for similar phase angle. Phase angles range from 33 degrees (Prometheus) to 86 degrees (Pan). The images were resized to a common scale and rotated so that illumination appears to be coming from the right.
Some information about the observations:
Here is a version without Mimas.