Cool tone / warm tone
The simple two-way split, cool tone or warm tone, often used as the entry point before narrowing to a season.
Cool tone and warm tone are the two-category version of the hue axis, the same warm-versus-cool question that underlies the full twelve-season system, but stopped at its simplest possible answer. The terms are used everywhere from beauty counters to Korean personal-color studios, where they translate directly from the Korean terms for warm tone and cool tone, to skincare shade-matching tools, usually as a quick first filter before, if at all, going further into a full season. A warm tone carries a yellow or golden undertone and tends to suit gold jewelry and yellow-based color; a cool tone carries a blue or pink undertone and tends to suit silver jewelry and blue-based color. The two-way split is fast and genuinely useful as a starting point, but it says nothing about value or chroma, so two people who are both warm tone can still need very different palettes once lightness and saturation are taken into account.
Why it matters
Cool-tone and warm-tone labelling is the fastest, most widely available color filter online, but it is only the first of three questions. Treating it as a full answer is how people end up with a warm wardrobe that still doesn't quite work.