Red lipstick, and finding your undertone

The universal red is a marketing position, not a colour. Reds in cosmetics are built from a narrow set of pigments that lean either towards blue or towards orange, and the two leanings behave differently against enamel, against skin and against each other. Knowing which side of that line you want is most of the decision. The rest is texture.

The palette is smaller than the counter suggests. Cool reds are carried by carmine and by the lake pigments in the crimson range, which hold a violet cast even at full opacity. Warm reds lean on iron oxide and on the more orange lakes, and they carry a brown that reads as heat rather than as dirt. A great many shades sold as true red are a blend of the two, balanced to sit near the middle, which is why they look convincing on a card and indecisive on a mouth. There is also the family of stains built on Red 27, which is colourless in the bullet and develops on contact with the pH of the lip, so the shade you approve is never the shade you applied. What separates them in use is not the lip but the teeth. Enamel is not white. It is a pale, faintly yellow, semi translucent material, and it is sitting a few millimetres from whatever you have chosen. A blue based red is close to the opposite of that yellow, so contrast pushes the enamel back towards white. An orange based red sits alongside the yellow, agrees with it, and lends it emphasis. This is a matter of adjacency, not of quality, and it is the reason an expensive warm red can look cheap on one person and correct on the next. Skin then decides how much warmth the shade can carry. The vein test is crude and often wrong under artificial light. More reliable is a plain white cloth held under the jaw in daylight, which will make the face read either yellow or pink against it. Olive skin is a third case rather than a warm one, since it holds a green cast that neutralises orange and can take a red far bluer than its depth suggests.

Pigment is only half of it. The same red dispersed into a matte base and into a gloss will read as two different colours, often a full step apart in both depth and temperature, because what reaches the eye is the surface as much as the particle underneath it.

A matte carries a high pigment load and a quantity of silica or treated filler to kill shine. That surface scatters light in every direction, so very little bounces straight back, and the shade reads deeper, flatter and a degree cooler than the pigment alone would suggest. A satin or a gloss holds the same pigment in esters and oils that form a smooth film, which reflects specularly, throws a highlight, and lifts the whole thing brighter and warmer. If a red has been rejected as too heavy, the objection is frequently to the finish rather than to the colour, and the identical pigment in a balm will pass without comment. Coverage matters for the same reason. A sheer red is a mixture, not a colour, since the natural pigmentation of the lip shows through and contributes. Lips that are already blue toned will drag a warm red cooler and duller. Lips with strong natural colour will overpower a pale coral entirely. Opacity is therefore a variable to be chosen rather than a virtue, and anyone testing on the back of the hand, where the skin is a different colour and a different texture from the mouth, is testing nothing. The test itself takes a minute. Put one candidate on the left half of the mouth and the other on the right, then walk to a north facing window and turn away from every lamp and every ring light, because those are tuned to flatter and will not tell you the truth. Look at your teeth first, not the lipstick. Whichever side makes the enamel look dull or yellow is the wrong side, and you will know within seconds. Then check the shadow beside the nose and along the jaw: the correct red leaves the face looking clearer, and the wrong one puts grey into the corners.