HSL qualifier

Pick a colour with the eyedropper and the qualifier builds a mask from everything inside that hue, saturation and brightness range. You then grade the selection on its own: cool a green wall, take the red out of a face, lift a brand colour while the rest of the frame stays put.

Edges are where it falls apart. A tight selection buzzes and crawls along its boundary, worst on skin and on compressed footage, so soften the matte and widen the range until the crawling stops. View the mask by itself before grading through it, because most bad secondary grades are bad selections nobody ever looked at.