HEX, RGB, CMYK, Pantone: What to Put in Brand Guidelines

Every brand book has a colour page. Most of them list four values per colour, in a neat row, as though those values are four spellings of the same word.

They aren't. They're four different systems, two of which describe light and two of which describe ink, and the conversions between them lose information in ways that cause real arguments with printers.

Here's what each one is for and what to actually put in the document.

The four systems, quickly

HEX is RGB in hexadecimal. #EE2E2D is just 238, 46, 45 written for CSS. If you list both HEX and RGB you have listed the same value twice — which is fine and conventional, because developers want HEX and everyone else finds RGB more readable, but understand you've specified one colour, not two.

RGB is additive. It describes light emitted by a screen. It's device-dependent: the same RGB triplet looks different on your monitor and the client's, unless both are calibrated and colour-managed, which they aren't.

CMYK is subtractive. It describes four process inks laid on paper. It is heavily dependent on press, ink set, and stock — the same CMYK build on coated and uncoated paper produces visibly different colour, which is why the same Pantone number has separate coated and uncoated entries.

Pantone is not a colour space at all. It's a catalogue of pre-mixed inks. PANTONE 185 C isn't a recipe you assemble from other inks; it's a specific ink that arrives in a can. That difference is the source of most of the confusion on this page.

Why you can't convert Pantone to HEX

You can produce a HEX value that sits near a Pantone ink. You cannot produce one that is it, and for a good number of Pantone colours you can't even get close.

Two reasons.

Gamut. A screen makes colour from three primaries. There are inks — most of the 800-series fluorescents, the metallics, plenty of the saturated oranges and greens — that fall outside what those three primaries can mix. No RGB triplet represents them, because the display physically cannot produce that colour. The conversion doesn't approximate; it clips.

Substrate. Pantone publishes different measured values for the same ink on coated and uncoated stock, because the paper changes the colour. A single HEX value has nowhere to put that distinction.

So when a tool offers to tell you the Pantone match for #EE2E2D, treat it as a suggestion for a starting point. It's a lookup against a table, not a measurement, and it cannot know which book you're printing to.

The honest way to express nearness is Delta E — a number describing perceptual distance between two colours. Under 1 is imperceptible to most people. Under 2 is generally accepted as a commercial match. Above 5 you're looking at a different colour. If a tool gives you a Pantone suggestion without a Delta E, it's telling you a conclusion without the evidence.

What actually belongs in the document

For each brand colour, list:

• Pantone, if the identity uses spot inks. Specify the book — 185 C and 185 U are not interchangeable, and "PANTONE 185" alone will get you a phone call.
• CMYK, as the process build for when spot printing isn't available or economical. Ideally supply separate coated and uncoated builds.
• HEX, for digital. One value.
• RGB, optional, since it duplicates HEX. Include it if your audience expects it.

And a line most guidelines omit and should include: which of these is authoritative. If the brand is defined by a Pantone ink, say so, and say that the CMYK and HEX values are approximations of it for contexts where the ink isn't available. If the brand was designed on screen and has no spot ink, say that — there's nothing wrong with a digital-first brand, but a printer needs to know they're matching to a CMYK build rather than hunting for an ink.

Without that line, every reproduction decision is a guess about your intent.

Spot versus process, in one paragraph

A spot colour is a single pre-mixed ink applied by its own plate. Consistent, exact, and it costs an extra plate. A process colour is simulated by overlapping cyan, magenta, yellow and black dots. Cheaper, universal, and slightly different every run.

Identity work often specifies spot for the logo and process for everything else. That's a reasonable default: the mark is the thing people recognise, so it gets the consistency, and the brochure body pages don't need it.

Getting the values out of your artwork

Two ways, with very different reliability.

Read them from the file. If a swatch in your Illustrator document is a spot colour, the file already knows its name. That's not an inference — the designer assigned that ink, and it's recorded in the document. This is the value you want, and it's the one to put in the guidelines.

Sample and convert. If you're picking colour off a rasterised logo or a JPEG, you're reading pixels that have already been through at least one conversion, possibly several, possibly with no colour management. Whatever you get out is a description of that file, not of the brand. It's fine for a rough start and it is not a specification.

The practical rule: if the artwork has spot swatches, use them. If it doesn't, the brand doesn't have a Pantone, and inventing one from a pixel value is how a colour quietly drifts across a rebrand.

Common mistakes

Listing a Pantone that isn't in the file. Someone ran a converter, liked the number, and wrote it down. Now the printer mixes an ink that doesn't match the artwork.

Omitting the book suffix. 185 with no C or U. Extremely common, always causes a query.

One CMYK build for every stock. Defensible for simplicity, but say that's what you've done, so nobody assumes it was measured for their paper.

Screenshotting the colour page. The values become unselectable, which guarantees somebody retypes them, which guarantees a transposed digit eventually.

Treating HEX as the master. Fine for a digital-only brand, actively wrong if there's a spot ink, because you've made the approximation the source of truth.

Doing this with GridMe

GridMe's Colour Code tool reads the colours off swatches you select in Illustrator and lays out labelled specimens — HEX, RGB and CMYK, positioned and styled to your settings.

Where a swatch is a genuine spot colour, it prints the ink name recorded in the document, exactly as assigned. Where a colour is process, it leaves that line out rather than guessing a Pantone, because a guess in a brand book is worse than a blank. There's an optional mode that will suggest the closest spot swatch already loaded in your own document, and it shows the Delta E alongside so you can judge the match yourself.

Download GridMe if you build colour pages regularly and would rather not transcribe values by hand.

The short version

Say what the colour is, say which value is authoritative, and don't promise a Pantone match you haven't measured. Everything else on the colour page is formatting.