Skin undertone

All skin is orange

In the CIE Lab colour space, every human complexion falls between roughly 45° and 75° of hue. That is a narrow band, and it is orange throughout. So the question undertone asks is never whether your skin is orange — it is where inside that band you sit.

Below 54° a complexion leans pink and reads cool. Above 62° it leans golden and reads warm. The 8 degrees between are neutral, which is a real category and a more populated one than most advice admits.

The three

• Cool undertone

  Skin sitting on the pink side of the narrow band every complexion occupies — below 54° of hue in Lab.

  Metals: Silver, white gold and platinum sit naturally against cool skin. Yellow gold can look brassy.

• Neutral undertone

  Between 54° and 62° of hue — neither pink nor golden dominating. More common than the internet suggests.

  Metals: Both silver and gold work. Mixed metals genuinely suit you, which is unusual.

• Warm undertone

  Skin above 62° of hue — golden or peach beneath the surface, with the redness to match.

  Metals: Yellow gold, copper and bronze. Silver can look flat or washed out.

Why the tests disagree with each other

Because the whole question lives inside eight degrees, and almost everything moves it more than that. A warm bulb pushes measured hue upward. A phone screen's white balance pushes it either way. A shop floor is lit to make products look appealing rather than accurate, which in practice means warm — and that is where most people are told their undertone.

The vein test reads blood colour through skin, filtered by however much melanin sits above it, so it works better on light skin than deep. The jewellery test is blunt but aimed at the right axis. The white paper test is the best of the three, because the paper supplies a neutral reference the eye otherwise lacks — which is the same thing our tool does with the whites of your eyes.

Olive is a separate axis

Olive is not a fourth undertone, and treating it as one is the commonest structural mistake in this subject. A complexion can be warm by hue and still read olive, because olive is about low chroma — how saturated the skin colour is — rather than about which way the hue leans. Our tool flags it when chroma falls below 18 rather than asserting it as a category.

An earlier version of our classifier derived olive from the ratio of the b* to the a* axis, which was simply wrong: that ratio is the tangent of the hue angle, so the rule was relabelling every warm complexion. It was caught by tests before it shipped.

What undertone feeds into

• Skin undertone finder — the hue angle measured directly, corrected for room lighting.
• The twelve colour seasons — undertone plus depth plus clarity.
• Foundation shade matcher — undertone plus depth, as a coordinate you can shop with.

What is measurable here is the hue of skin in a colour space. Which colours anyone prefers is a matter of taste, and nothing here scores or ranks anyone's appearance.