The controversy about color Mars lander image calibration, begun in 1976 during the Viking mission, continues with the 2004 Spirit and Opportunity missions. Officially released color images at web site "Photojournal.JPL.NASA.Gov" continue to show wide variation. Two sets of filters are used by NASA to produce color images from Spirit. One conventional set of red, green and blue filters has been used for images of the calibration chart alone and small pieces of the soil. Another set of infra-red, green and blue filters is used for larger panoramic images. While most objects in the Martian scene are not affected by this change, the appearance of the color calibration chart changes drastically. An extreme example of this can be found in the comparison of the blue color panel using the two different sets of filters. When the blue panel is seen in the panorama images, it appears to be bright red. Small blue wire ties on the rover also appear to be bright red in the panoramas. NASA claims that the blue color panel is unusually reflective in the near infra-red. This makes inspection of the color balance more difficult and many problems exist in published "true color" images. This paper will round up this and other issues involving Spirit color image calibration.
Ron L. Levin, Ron L. Levin,
"Color calibration of Spirit and Opportunity rover images", Proc. SPIE 5555, Instruments, Methods, and Missions for Astrobiology VIII, (1 November 2004); doi: 10.1117/12.562375; https://doi.org/10.1117/12.562375