A reconstruction of Io's true color
explaining image processing,
amateur image processing,
The left image is a straight red-green-violet color combination from Galileo. The right image has a blue channel synthesized from blue and green filter images (blue = 0.55*green + 0.45*violet) and may be a closer representation of the color that Io would appear to the human observer.
NASA / JPL / UA / color composite by Jason Perry
Original image data dated on or about March 29, 1998