@Wolfgang 's version “my take…” is just a bit more natural.
HSL, by dragging the pins around you can select more carefully a group of colors
1 use colorpicker for the initial colorselection.
2 shift saturation to -100 (selection gets grey) (if not visible enough shift lumination to 100.
3 use pins to get all you want “grey”.
4 check by choose a daft color the selection (first set sat and lum back to 0)
5 adjust accordenly in what you see.
6 double click on colorpin (outer wheel) to reset colorchange choice and use the three sliders saturation, lumination and uniformity to finalize desired color.
7 pick one of the other channels and proceed for say “red” repeat step 1 to 6.
Clearviewplus has some “intelligents” in choosing where to place microcontrast to enhance sharpening and saturation.
see this post to see which slider and contrast type does what.
Have Fun!