Approaching Callisto (Absolute Natural Colors; credits for the additional process. and color.: Dr Paolo C. Fienga/Lunar Explorer Italia/Italian Planetary Foundation)

Bright scars on a darker Surface testify to a long history of impacts on the Jovian moon Callisto, as it can be seen in this image obtained by the NASA - Galileo Spacecraft. The picture, taken in May 2001, is the only complete global Absolute Natural Color image of Callisto ever obtained by the NASA - Galileo Spacecraft, which orbited around Jupiter from December, 7, of the AD 1995 and until September 21, of the AD 2003, when the Spacecraft was destroyed during a controlled impact with Jupiter itself.
Of Jupiter's 4 (four) largest moons (also known as the "Galilean Moons"), Callisto orbits farthest from the Giant Gas Planet. Furthermore, Callisto's Surface is uniformly cratered but, as you can see for yourself, is not uniform in color or brightness at all. At present day, Planetary Scientists believe that the brighter areas are mainly Ice while the darker ones should be made of highly eroded (and Ice-poor) Rocky Materials.

This frame (which is an Original NASA - Galileo Spacecraft color frame published on the NASA - Planetary Photojournal with the ID n. PIA 03456) has been additionally processed and then re-colorized, according to an educated guess, by Dr Paolo C. Fienga (LXTT-IPF), in Absolute Natural Colors (such as the colors that a human eye would actually perceive if someone were onboard the NASA - Galileo Spacecraft and then looked outside, towards the Jovian moon Callisto), by using an original technique created - and, in time, dramatically improved - by the Lunar Explorer Italia Team. Different colors, as well as different shades of the same color, mean, among others, the existence of different Elements present on the Surface of Callisto, each having a different Albedo (---> Reflectivity) and Chemical Composition.