Shared (every palette-coloured scene — and the backdrop)

Param	Default	What it does
hue	0.0	Rotates the gradient sample coordinate (the pre-existing hue knob). Scene only.
saturation	1.0	Scales chroma toward luma. 1 unchanged, 0 grayscale, >1 oversaturated.
palette_mix	0.0	A/B crossfade position (see below); 0 = palette A.
palette_steps	0.0 (off)	Quantizes the gradient into that many hard bands — see Hard bands.
palette_contour	0.0 (off)	Draws a hairline at each band edge where the ink actually changes. The six continuous-field scenes only — analytic_field, cellular, fragment_field, reaction_diffusion, shape_field, warp_mesh; inert elsewhere, and nothing warns — same section.
palette_contour_style	0	What that hairline is: 0 a soft darkening, 1 a hard one, 2 a soft line in the palette’s own colour, 3 a hard one. Declared by the six scenes above and unknown anywhere else, so a typo there warns.
palette_contour_ink	0.0	Where along the palette styles 2 and 3 take their colour — an absolute coordinate hue does not shift. Same six scenes.

saturation and palette_mix are one binding with two consumers: the active scene and the background pre-pass. You write them once and the whole frame answers — see the backdrop. hue is the exception, and deliberately: it offsets the scene’s sample coordinate, and the backdrop has its own coordinate in bg_hue.