Warm vs cool undertones

Every color page here labels its color warm, cool or neutral. This is how that label is arrived at, what it is good for, and where it stops being enough.

What an undertone actually is

Most paint colors are not a pure hue. They are a dominant impression with a smaller bias underneath it - the grey that goes slightly green, the white that goes slightly yellow. That bias is the undertone, and it is what decides whether two colors sit together or fight.

It matters most in the colors that barely look like colors. Nobody is surprised by what a saturated red does. An off-white with a green bias next to an off-white with a pink bias, on the other hand, will make one of them look dirty, and neither chip predicted it.

How this site decides

The label is not read off the color’s name. Names are marketing, and “Silver Sage” tells you nothing testable. Instead:

Every color’s hex is converted to CIE L*a*b* (D65) and then to L*C*h° - lightness, chroma (how much color there is) and hue angle.
If chroma is below 8, the color has no meaningful hue at all: it is a white, a grey or a black, depending on lightness, and it is labelled neutral.
Above that, the hue angle selects a family. Greens, teals, blues and purples are cool. Reds, oranges, yellows, beiges, browns and pinks are warm.

Because the undertone is derived from the family, the two can never disagree on a page: nothing here is described as a “cool yellow”.

Two things follow from that. The classification is measured, so it is consistent - every brand is treated the same way, which is what makes cross-brand comparison mean anything. And it is coarse on purpose: three labels over thousands of colors is a sorting tool, not a verdict.

Greige, and the honest limits

The hard cases are the low-chroma warm colors - the beiges, greiges and off-whites that most interior paint actually consists of. A color at chroma 9 scrapes past the neutral threshold and gets called warm; one at chroma 7 does not. On a wall you will not see a cliff there, and two colors either side of the line can look like the same paint.

So use the chroma figure, which is on every color page, alongside the label:

Chroma under 8 - no real cast. It will take its character from whatever is next to it.
Chroma 8-25 - a soft, muted cast. This is where most greiges live, and where the light in the room decides what you get.
Chroma 25-50 - a clear, definite color.
Above 50 - strongly saturated; the undertone question stops being subtle.

The second limit is that a hue angle is a single number and an undertone is a comparison. “This grey is green” is really “this grey is greener than the grey next to it”. Which brings us to the only reliable test.

Checking an undertone yourself

Compare, never look alone. Put the sample next to a known reference - a sheet of printer paper for warmth against near-white, or two or three candidate colors side by side. A single chip against a wall you already dislike tells you nothing.
Look at the darkest color on the same strip. Manufacturer strips are usually the same colorant mix at different strengths, so the bottom chip exaggerates the undertone the top chip is hiding.
Look at all the light you actually have. Daylight at noon, daylight at dusk, and your bulbs at night. A warm bulb pushes a beige noticeably yellow; cool daylight pulls a purple toward grey. This is not the paint changing its mind - it is the light having a different spectrum, and no number on this site predicts it for your room.
Beware of surroundings. Foliage outside a window pushes green into everything, and a strong carpet colour bounces up onto the walls.

Using it here

The search page filters by undertone across every brand at once, and combines it with family, brand and LRV - “warm neutrals above LRV 60” is one query. The cool families are the blues, teals, greens and purples, and the neutrals are the whites, greys and blacks.

The usual caveat applies harder here than anywhere: screens emit light and paint reflects it, so an undertone on a monitor is a hint, not evidence. Get a sample. See how cross-brand matching works if you are comparing a color across two brands.

Common questions

What is a paint undertone?

An undertone is the smaller colour bias sitting under a paint's dominant impression - the grey that leans green, the white that leans yellow. It matters most in the colours that barely look like colours, because that bias is what decides whether two of them sit together or fight.

How do you tell if a paint colour is warm or cool?

Hold the chip against a sheet of pure white paper: the bias that appears against true white is the undertone, and it is invisible against a wall or another chip. On this site the label is computed instead of judged - the hex is converted to CIE L*a*b*, and the hue angle and chroma decide warm, cool or neutral, so the name of the colour never enters into it.

What undertone does a particular white have?

Every colour page states its undertone next to its Lab, LRV and hex values, so a white that reads yellow, pink or green is labelled rather than guessed at. Whites are where undertone matters most: they carry so little chroma that the bias is the only thing distinguishing one from another.

Why do two whites look wrong together?

Because their undertones oppose each other. A green-biased white beside a pink-biased one makes one of the two look dirty, and neither chip predicted it on its own. Compare the undertone labels before pairing trim, ceiling and wall whites, not the names.

Can a paint colour have no undertone?

Effectively yes. A colour with very low chroma has no bias strong enough to read as warm or cool, and is labelled neutral here. True neutrals are rarer than paint names suggest - most colours sold as neutral carry a measurable lean one way or the other.

Do undertones change under different lighting?

The measured undertone is fixed; what you see is not. North light is cool and pulls a colour further that way, incandescent and warm LEDs push it back, and a strong wall or floor colour nearby bounces its own bias onto the paint. This is why a sample has to be viewed in the room it is for, at the hours you use it.