Colour methodology
In a category full of unsourced colour claims, showing the work is the differentiator. Here is exactly where every number on a colour page comes from.
Hex values
Every hex on this site is manufacturer-published. Sherwin-Williams publishes its deck as an official PDF of colour number, name and RGB; that document is our source of record and is cited on each colour page with the date we accessed it. We do not take hex values from colour blogs or aggregators — those disagree with each other and with the manufacturer.
LRV
LRV is the percentage of visible light a surface reflects. Where the manufacturer publishes an LRV for a colour, we show their figure as primary and ours as a cross-check. Where they do not, we compute it and label it computed everywhere it appears.
Our computed value is the WCAG 2.2 relative luminance of the manufacturer's sRGB hex, multiplied by 100. That is the standard screen-side approximation. It is not a spectrophotometer reading of a physical chip, and the two do not agree exactly.
How far apart they are, measured
For the colours where we hold both figures, our computed LRV runs consistently about 0.8 to 0.9 points higher than the manufacturer's published value. Agreeable Gray SW 7029 is published at 60.386 and computes to 61.26. Alabaster SW 7008 is published at 82.215 and computes to 83.03.
The direction is consistent, which suggests a systematic difference in method rather than noise — a measured chip includes surface and gloss effects a pure sRGB calculation cannot capture. We publish both rather than quietly reconciling them.
A second discrepancy worth naming
Sherwin-Williams' bulk RGB PDF and its individual colour pages do not always agree to the digit. SW 7029 is #D2CDC2 in the PDF and is reported as D1CBC1 on the colour page — about one unit per channel. We use the PDF throughout so that all 1,500+ colours come from one consistent manufacturer source rather than a mix.
Undertone
Undertone is classified from the OKLCh hue angle of the manufacturer hex, not from HSL. OKLCh is perceptually uniform, so equal numeric steps look like equal visual steps — which matters enormously at the very low chroma where neutrals live and where casual colour vocabulary breaks down.
We only claim an undertone when chroma is high enough for it to be real. Below a chroma of 0.012 the honest answer is "effectively neutral", and that is what we say. Between 0.012 and 0.035 the undertone is present but subtle. Above that it is clear. A saturated colour is simply that colour — describing a strong blue as "having a blue undertone" is filler.
Families
Family thresholds are stated rather than implied, because "is 78 LRV a white or an off-white" is a genuine judgement call. Whites are LRV 82 or above at near-zero chroma; off-whites are 82+ with visible chroma, or 70+ at subtle chroma. Greiges are the warm, low-chroma band above LRV 45. The exact rules are in the build source.
Why screen colour is approximate
A swatch here is a CSS colour value, never an image — a JPEG chip is colour-shifted by compression before you ever see it. But even a perfect sRGB value is filtered through your display's calibration, brightness and colour profile, and paint on a wall behaves differently again under real light at real angles. On wide-gamut displays we serve the colour in oklch() with the sRGB hex as fallback, which renders closer to the physical chip on a P3 screen.
None of that makes a screen a substitute for a physical sample. Order one before you commit.
Trademarks
Colour names, codes and systems are trademarks of their manufacturers. We present them as editorial reference, attribute them, and link to the official colour page. We do not reproduce full colour charts as images.