Specification
The data sheet. Every figure here is computed from the
published files and can be recomputed from them — nothing on this page is
an estimate.
What the library contains
| Edition | 2026-08 |
| Colours | 4253 |
| Neutrals | 36 |
| With an English name | 4253 — all of them |
| Subsets | Basic 500 · Essential 2000 · Full 4253, nested |
Measurement
| Instrument | X-Rite i1Pro 3 |
| Geometry | 45°/0° — one angle. Colorimetry only: no metallic, pearlescent or otherwise goniochromatic effect is measured or represented, and no name in the library promises one. A finish that changes with the viewing angle would need an integrating sphere or a multi-angle instrument; a colour word naming a metal — gold, silver, copper — names a hue and a lightness read off a flat drawdown. |
| Spectral range | 380 – 730 nm |
| Interval | 10 nm — 36 readings per sample |
| Measurement conditions | M0, M1 and M2 — all three measured, none inferred |
| Backing | white |
| Substrate | one stock throughout, OBA index 6.46 |
| Repeatability | about 0.03 ΔE00 re-reading one patch without moving the instrument |
Colour specification
| Codes derived at | M2, D50, 2° |
| Illuminants offered | A, B, C, D50, D55, D60, D65, E, F2, F7, F11 |
| Observers | CIE 1931 2° and CIE 1964 10° |
| Difference formula | ΔE00, kL:kC:kH = 1:1:1 |
| Computed from | the spectrum, for every illuminant and observer except the published D50/2°, which is the measurement |
Extent
| Lightness | L 4.34 – 94.39 |
| Chroma | C 0.04 – 112.75 |
| Hue | 36 bins of 10°, all populated — between 90 and 153 colours each |
The theoretical range of L is 0 to 100. This library is made of printed
samples, so it stops where ink and paper stop.
Spacing
The library is built to a band, and both ends of it hold.
| Closest pair | 1.50 ΔE00 |
| Average to nearest neighbour | 2.52 |
| 95% within | 3.46 |
| Widest gap | 4.03 |
| Neutral ramp step | 1.90 – 2.00 |
No two colours closer than 1.5, none further than 4.0 from its
nearest neighbour. Close enough that the steps look even, wide enough
that the book stays a usable size. The distribution, and what each subset is
worth: Subset Statistics.
Display gamuts
How much of the library each display standard can show, computed from the
colorimetry rather than from a profile.
| Standard | Colours | Share |
|---|
| sRGB | 3258 | 76% |
| Display P3 | 3819 | 90% |
| Rec. 2020 | 4164 | 98% |
| outside all three | 95 | 2% |
Which is why the browser paints its swatches from CIELAB rather than from a
clipped hex value: on a wide-gamut display roughly a fifth of the library is
shown correctly that could not be otherwise. For print reproducibility see
Ranges instead — a different question with
very different answers.
Distribution
| Formats | CxF (ISO 17972-1), CGATS.17, Adobe Color Book, Adobe Swatch Exchange |
| Live data | a manifest and immutable versioned files — no token, no rate limit |
| Editions | immutable; a published colour’s code and spectra never change |
| Retired codes | never reissued |
What is not on this page. Why M2, what the illuminants do, what a
ΔE figure feels like — those are in
Learn. This page is
numbers.
How This Library Was Made is
where the numbers come from, including what is known to be imperfect.