HSL curves: bracket a colour, then hue, saturation or lightness
One point drags the whole line. Three points move only what sits between them.
Four curves across the top: luma/RGB, hue vs hue, hue vs saturation, hue vs lightness. Two boundary points plus a middle point isolate a range; the colour buttons along the bottom drop a safe set of three per colour; a histogram overlay shows how much of each hue is present (find the sky peak); click a colour in the viewer for a tight three-point set; Hue Rotate for fine hue moves. Big hue-vs-lightness moves band on 8-bit and smooth skies. Recolour an object: Alt+S, click it on hue vs hue, drag; a tracked mask cleans spill. Looks: pop = saturation and lightness together (either alone looks wrong); golden-hour greens toward yellow; teal blues, then lower their saturation; desaturated greens (+ darker on hue vs luma); teal-and-orange - yellows/greens toward orange with more saturation, watching the vectorscope, desaturating what would look unnatural; colour contrast between neighbours (yellow vs orange nudged apart); fix a LUT's colour on a node before the LUT; dramatic sky - cyan and blue buttons pulled down, lifted toward purple if the clouds go muddy.
The surgical tool; also the first place to look when a LUT does one thing wrong.