Folds the tonal range back on itself repeatedly, giving the metallic, oil-slick colours of a solarised photograph.
Each pixel's brightness is multiplied by amount and fed into a wave. Because a wave rises and falls forever, brightness values that were far apart can come out identical, and a smooth gradient turns into a series of bands. Raising amount packs more bands into the same range of tones.
colorMode changes the character completely. In mono the picture is reduced to brightness first, so the bands follow its tonal structure and everything comes out grey. In rgb each channel is folded on its own, and since the three channels rarely hold the same value, their bands land in different places. That disagreement is where the colours come from: nothing is being tinted, the channels have simply stopped agreeing with each other.