A common assumption in image processing is that the difference between two color channels of the same scene are band-limited.
For instance, the interpolation method used in Hirakawa's paper introducing Adaptive Homogeneity-directed Demosaicing fundamentally uses the assumption that (G-R) and (G-B) images of the same scene will be bandlimited relative to R, G and B images.
This assumption is also used to motivate decomposing video signals into Luminance/Chrominance components to save on data rate.
I feel like I am missing something very simple here. What justifies this assumption, and can it also be made for (R-B)?