Color-Dichotomy on Japetus (False Colors; credits: NASA/JPL/Space Science Institute)

Caption NASA:"Three different false-color views of Saturn's moon Japetus show the boundary of the so-called global "Color Dichotomy" on the Hemisphere of this moon facing away from Saturn.
Such a "Color Dichotomy", which has been detected in images from the Cassini Imaging Team, is a second global pattern found on Japetus besides the well-known global "Brightness Dichotomy".

This image consists of three panels, each of which was contrast-enhanced in different ways to bring out Surface Features. Minimal enhancement was applied to the image on the left panel while those on the middle and right panels were enhanced more (with contrast increased by factors of two and four, respectively), making them appear brighter and overexposed.
In the case of Japetus' Brightness Dichotomy, the Dark Terrain extends towards its Trailing Side at Equatorial Regions, while the Bright Terrain extends towards Japetus' Leading Side in the Polar Regions (see PIA11116).

In the case of the Color Dichotomy seen here, its boundary is quite well correlated with the boundary between Japetus' Leading and Trailing Hemispheres. At Near-InfraRed wavelengths, the Bright Terrain on the Leading Side is redder than the one visible on the Trailing Side. This pattern is visible in the panel on the left, which uses normal contrast enhancement. The characteristic reddish distribution also appears on the dark material, as seen in the middle and right-hand panels that have been adjusted with even higher contrast.

Indeed, the otherwise uniformly dark material shows different color hues, depending on whether the viewer looks at the Leading vs. the Trailing Side.
Cassini scientists think this effect is caused by material falling onto Japetus from the outer irregular moons of Saturn. (see PIA06145 to learn more)

Images obtained with InfraRed, Green and UltraViolet Spectral Filters (centered at 953, 563 and 338 nanometers, respectively) were combined to create these False Color views. The color seen here is similar to that produced in (red, green and blue) Natural Color views.

North on Japetus is approx. up in these images. The images were taken with the Cassini Spacecraft narrow-angle camera on Oct. 15, 2004. The view was obtained at a distance of approx. 1,2 MKM (such as about 746.000 miles) from Japetus and at a Sun-Japetus-Spacecraft, or Phase, Angle of 88°.
Image scale is roughly 7 Km (a little more than 4 miles) per pixel".