Here are histograms of the normalized red color component versus the normalized blue color component for the light gray world corrected test images. "Normalized red" refers to the "red" sensor value for a pixel, minus the luminance value (contributed to by all sensors) for that pixel.

The red channel is represented along the vertical axis, and the blue channel along the horizontal. The range of the horizontal (blue) channel is -128 to 64, and the range of the vertical (red) channel is -64 to 64.

Color Histograms of light gray world

Gamut	Illuminant A	Illuminant B	Illuminant C
All
Little Blue
Little Red

Evident in the above histograms is the effect of poor illumination in the blue sensor channel and the high gain needed to compensate -- the black vertical stripes.

Histograms in sensor space (instead of this chromaticity space) are also available.

Also available for comparison are the histograms of the original images in the same sensor space.

Finally, the simple Isis script used to histogram the images is hist.isis.