Palette tools and design systems use terms interchangeably that mean different things. Here is the vocabulary, with the distinctions that actually change what you produce.
Hue — position on the colour wheel, 0-360 degrees. Red near 0, green near 120, blue near 240. Changing hue changes which colour it is.
Saturation (HSL/HSV) and chroma (LCH/OKLCH) both describe colourfulness, but not identically. Saturation is relative to the maximum possible at that lightness; chroma is absolute. This is why two HSL colours at 100% saturation can look wildly different in intensity while two OKLCH colours at the same chroma look consistent.
Lightness versus brightness/value — lightness (the L in HSL and OKLCH) runs from black to white with the pure colour at the midpoint; value (the V in HSV) runs from black to the pure colour. They are different scales, which is why the same hex looks different in two pickers.
A tint is the colour mixed with white. A shade is mixed with black. A tone is mixed with grey, which lowers saturation without going all the way light or dark. A ramp or scale is the ordered set of these, conventionally numbered 50 (lightest) to 950 (darkest) with 500 as the base.
sRGB — the default web colour space; hex and rgb() live here. Display P3 — a wider gamut supported by most recent screens, reachable in CSS with color(display-p3 …), giving noticeably more vivid reds and greens. Gamut — the range of colours a space or device can represent; a colour outside the gamut is clipped to the nearest reproducible one, which is why an out-of-gamut OKLCH value can render duller than expected. OKLab / OKLCH — a perceptually uniform space where equal numeric steps look like equal visual steps, which is exactly what HSL fails at.
Contrast ratio — a number from 1:1 to 21:1 derived from the relative luminance of two colours. WCAG AA requires 4.5:1 for normal text and 3:1 for large text (24px regular or 18.66px bold and above) and for the boundaries of interactive components. AAA requires 7:1 and 4.5:1 respectively. Relative luminance is the weighted brightness calculation behind the ratio, weighting green most heavily because human vision does. APCA is a newer contrast model that better matches perception, particularly for light text on dark backgrounds, but WCAG's ratio remains the conformance requirement.
Primitive tokens name raw values (--orange-500). Semantic tokens name roles (--color-surface, --color-danger) and point at primitives. Components should only ever reference semantic tokens — that indirection is what makes dark mode and rebranding a change in one file. Alpha is opacity; colour-mix blends two colours in a named space, so color-mix(in oklch, var(--brand) 20%, white) produces a tint that stays on-hue.