Skin
undertones

Undertone is not skin tone

Skin tone is how light or deep you are, and it moves through the year. Undertone is the cast sitting underneath it, and it does not move — not with a tan, not with hair dye, not with age. That is why a foundation can be exactly the right darkness and still look wrong: the depth matches and the colour underneath does not.

There are four worth naming. Warm leans gold or peach. Cool leans pink or blue. Neutral holds neither strongly. Olive carries a faint green over a warm base, at any depth of skin. Every one of the four occurs across the whole range from the fairest skin to the deepest, which is the single most commonly missed fact about the subject.

The four undertones

Reading yours at home

Three tests, in daylight, on bare skin, with your hair tied back. Each one is testing something slightly different, which is why it is worth doing all three rather than trusting whichever gives the answer you expected.

• — Jewellery. Hold gold against your jaw, then silver. One lifts the face and one drains it. This is the most reliable of the three, because you are judging your face rather than your wrist and the comparison is direct.
• — White paper. Hold a plain white sheet beside your bare face. Against true white the cast has nowhere to hide: you will see yellow, pink or a grey-green.
• — Veins. Turn your wrist over and look. Green suggests warm, blue or purple suggests cool. This is the least reliable of the three, because thin skin, cold hands and indoor bulbs all move the answer.

If the three disagree, you are probably neutral or olive. Those two are the ones the home tests handle worst, and they are also the two that explain most unexplained bad foundation matches.

Measure it rather than guess

Judging a cast by eye means judging a colour against whatever is in the room with you, which is exactly what the eye is worst at. The undertone finder reads two patches of cheek from a photograph, discards the pixels that are shadow, shine or hair, and measures where the remaining colour sits on the yellow-to-blue axis that colour science uses. It runs in your browser, it is free, and the photograph is never uploaded.