It’s more or less linear—what you can do is dither in each of the R,G,B channels separately. To remove banding in an image, you dither in R, dither in G, dither

It’s more or less linear—what you can do is dither in each of the R,G,B channels separately. To remove banding in an image, you dither in R, dither in G, dither in B. If you take a gray value that is 50% between two gray values, and you use uncorrelated noise to dither, then the result will contain all (±0.5,±0.5,±0.5) delta from the original gray. If you use ordered (correlated) dither, you’ll get a subset of those 8 colors.