How close is a paint dupe, really? The measurement behind every match

Every paint dupe site tells you its matches are accurate. Almost none of them tell you how accurate, which colours are not, or what the number means. Here is ours, across all 5,336 colours we have measured, including the half that do not come out well.

What is actually being measured

A trade merchant cannot mix "Farrow & Ball Hague Blue". What they can mix is an NCS code, an international standard that describes a colour by its blackness, its chromaticness and its hue. So every colour on this site is tied to the NCS shade its tin would be mixed to, and then we measure the gap between the original colour and that shade.

The measurement is CIEDE2000, usually written dE. It is the colour industry's answer to a hard question: two pairs of colours can differ by the same amount on paper and look nothing alike to a person, because the eye is far fussier about some shifts than others. CIEDE2000 weights the difference the way human vision does. One dE is roughly the smallest difference a trained eye can catch under good light, with the two samples touching.

The four grades

• Exact NCS match (under 1 dE): closer than the eye can tell apart. 557 colours. Farrow & Ball Setting plaster sits at 0.25 dE.
• Close NCS match (1 to 2 dE): a difference you would only see with the two side by side. 2,102 colours. Farrow & Ball Blackened sits at 1.02 dE.
• Slight NCS shift (2 to 3.5 dE): a slight shift in tone against the original, worth checking with a tester. 2,199 colours. Farrow & Ball Calluna sits at 2.01 dE.
• Nearest NCS shade (over 3.5 dE): the closest standard NCS shade rather than a like for like match, so test it on the wall first. 478 colours. Farrow & Ball Paean black sits at 4.7 dE.

The whole catalogue, graded

Across 5,336 measured colours, 2,659 land within 2 dE of the shade their tin is mixed to. That is 50%. The median colour sits at 2.01 dE, a quarter are tighter than 1.43, and the worst in the catalogue is 8.89 dE out.

Share of each brand's range landing within 2 dE of the NCS shade it is mixed to. Ordered by that share, not by how well known the brand is.

Brand	Colours	Within 2 dE	Exact	Nearest shade only
Earthborn	120	68%	19	7
Fired Earth	120	57%	17	10
Coat	118	53%	11	10
Craig & Rose	110	53%	14	8
Little Greene	262	51%	34	24
Benjamin Moore	2,549	51%	267	204
Farrow & Ball	281	50%	29	23
Sanderson	152	50%	24	10
Sherwin-Williams	1,525	46%	135	176
Lick	99	45%	7	6

Why half the range misses

NCS is a standard with a finite number of shades. Paint companies are not designing to it, they are designing to sell a colour, and a colour mixed in a factory lands wherever the pigments put it. When that point falls between two NCS shades, the nearest one is the nearest one, and no amount of wanting it to be closer will move it.

That is why we grade rather than claim. A colour at 0.4 dE and a colour at 3.9 dE are both honestly described as matches somewhere on the internet today. They are not the same proposition, and you should be told which one you are buying before the tin arrives.

What the number does not cover

The dE figure is about colour, and only colour. It says nothing about finish, and finish changes what you see: the same colour in a dead flat matt and in an eggshell will read differently on the same wall, because one scatters light and the other returns it. It says nothing about opacity or how many coats you will need. And it says nothing about your room, which is the variable that beats all the others. North light is cool and will pull a warm neutral grey. A south-facing afternoon will push it the other way.

So treat the grade as what it is: the part of the question that can be measured, measured properly, instead of an adjective. Then put a tester on the wall, because the rest of the question cannot be answered from a table.