How to find your undertone, and why it is not your skin colour
4 August 2026 — 6 min read
Skin colour is the shade you see. Undertone is the cast underneath it — the quiet blue, gold or green that does not move when you tan, lighten, flush or age. It is the reason two people with identical foundation shades on paper can look wrong and right in the same bottle.
There are four undertones worth naming: cool, warm, neutral and olive. Cool leans blue or pink. Warm leans gold or peach. Neutral holds neither strongly. Olive carries a faint green that sits over any depth of skin and is the one most often mistaken for “sallow”.
The vein test, and what it is really showing
Turn your wrist over in daylight and look at the veins. Blue or purple suggests cool. Green suggests warm. A mix, or a colour you cannot commit to, suggests neutral or olive.
It works because you are looking at blood through skin, and the skin is filtering it. What you are reading is the filter, not the blood. It is also the least reliable of the four tests: thin skin, cold hands and artificial light all move the answer.
The jewellery test
Hold silver against your face, then gold. One will make your skin look lit; the other will make it look tired. Silver flattering you points cool. Gold points warm. Both looking fine points neutral.
This one is better than the vein test because you are judging your face rather than your wrist, and because the comparison is direct — you are not remembering the first result while you look at the second.
The white paper test
Tie your hair back, take off any makeup, and hold a sheet of plain white paper next to your bare face in daylight. Against true white, the cast in your skin has nowhere to hide.
- Pink, red or bluish against the paper — cool
- Yellow, gold or peach — warm
- Grey or faintly green — olive
- No obvious cast either way — neutral
How you burn
Skin that burns quickly and rarely holds a tan tends to be cool. Skin that tans easily and burns slowly tends to be warm. It is a tendency and not a rule, and it says nothing about depth — deep skin can be cool, fair skin can be warm.
Why it matters more than the shade number
Foundation is the obvious one: a warm foundation on cool skin reads orange, a cool foundation on warm skin reads grey. But it decides more than base. Cool undertones tend to wear berry, rose and true red well. Warm undertones tend to carry coral, brick and terracotta. Olive skin often looks best in shades that would flatten someone else — brick, bronze, muted plum.
None of this is a rule you have to obey. It is a starting point that saves you three wrong lipsticks.
What Boirelle does with it
The app reads undertone from your selfie along with six other things, and orders the shade palette in the try-on studio so that whatever suits your undertone comes first. When it cannot read your undertone confidently — bad light, heavy makeup, a photograph too dark to judge — it says so and prints a dash rather than picking one for you.