Hexachrome: The Six-Colour Printing System

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The Limitations of Standard CMYK

Standard four-colour process printing — CMYK (Cyan, Magenta, Yellow, Black) — is the foundation of commercial printing. By overprinting halftone dots of these four inks at varying densities, a press can reproduce a wide range of colours. But the CMYK gamut has well-documented limitations. The most obvious are in the regions of vivid oranges, saturated greens, and bright blues: these colours lie outside what CMYK inks can physically reproduce. The magenta and yellow inks used in CMYK, when combined, produce an orange that is decidedly muted compared to a vivid Pantone orange. Similarly, cyan and yellow produce a green that falls far short of a saturated natural green or a vivid Pantone equivalent.

For much commercial work — everyday brochures, office documents, general advertising — this is an acceptable limitation. But for premium packaging, food photography, fashion, automotive advertising, and fine art reproduction, the CMYK gamut gap is a real problem. It is also a problem for brand owners who need to reproduce a specific Pantone spot colour in process printing and find that the CMYK equivalent looks dull or shifted.

What Hexachrome Is

Hexachrome is a six-colour extended-gamut printing system developed by Pantone and introduced in 1994. It adds two ink channels to the standard CMYK four: Orange (O) and Violet (V), giving the process the designation CMYKOV. The choice of orange and violet was deliberate: these two inks fill in the specific regions of the colour spectrum where standard CMYK is weakest, dramatically expanding the total printable gamut.

By adding a dedicated orange ink, Hexachrome can reproduce the vivid warm oranges and certain reds that CMYK struggles with. By adding a violet ink, it gains access to cleaner purples and certain blues that are also problematic in standard CMYK. Together, the six inks allow Hexachrome to reproduce approximately 90% of the Pantone Matching System colour library as a process ink combination — a dramatic improvement over the roughly 50–60% achievable with standard CMYK. This means that for many jobs where a designer would previously have needed to run a job with CMYK plus two or three Pantone spot colour inks to cover the brand colours, Hexachrome can reproduce those colours without the additional spot ink stations.

How Hexachrome Expands the Printable Gamut

The gamut expansion Hexachrome provides is significant when visualised in a CIE colour space. The standard CMYK gamut — the envelope of colours achievable with a given set of CMYK inks on a given paper — looks roughly like an irregular pyramid when plotted in three dimensions. The Hexachrome gamut is substantially larger, particularly in the orange-red and green-blue quadrants of the colour space, which correspond exactly to the orange and violet ink additions. For a designer soft-proofing a food photography image containing vivid peppers or exotic fruit, the difference between CMYK and Hexachrome rendering is immediately visible.

Hexachrome inks were also formulated to be purer (higher chroma) than standard CMYK process inks, which contributes further to the expanded gamut. The cleaner the primary inks, the larger the gamut they can define when combined.

Applications and RIP Support

During the mid-1990s and early 2000s, Hexachrome attracted support from a range of applications and RIP vendors. Adobe InDesign and Adobe Illustrator both shipped with Hexachrome swatch libraries, allowing designers to specify CMYKOV colour values directly. Harlequin, the major RIP vendor, implemented Hexachrome colour separation support. Prepress software from EFI and other vendors also included Hexachrome workflows.

In terms of output devices, Hexachrome required either a six-unit offset press (or a press with additional ink stations beyond the standard four) or certain wide-format inkjet printers that supported extended ink sets. This was not a trivial requirement: most commercial printers run four- or five-colour presses, and adding two additional ink stations requires both hardware investment and press time.

In PDF, Hexachrome colours were represented using the DeviceN colour space — a generalised multi-channel colour space type that can name and specify any number of colorants. A DeviceN colour space for Hexachrome would name the six channels (Cyan, Magenta, Yellow, Black, Orange, Violet) and include an alternate CMYK or ICCBased space for fallback rendering on devices that could not handle the full six-colour output.

Pantone Discontinuing Hexachrome in 2008

Despite its technical merits, Hexachrome never achieved mainstream adoption. The requirement for six-ink press capability limited it to printers willing and able to invest in the additional infrastructure. The cost premium over standard CMYK was significant. And for most jobs, the improvement was not sufficient to justify the expense.

Pantone officially discontinued the Hexachrome system in 2008, ending new development and effectively withdrawing it from active promotion. The decision reflected commercial reality: the installed base of Hexachrome-capable presses and workflows was too small to sustain the system as a mainstream offering, and alternatives — particularly high-quality spot colour workflows combined with standard CMYK — were proving sufficient for most high-end print needs.

Software support followed: newer versions of Adobe applications no longer include Hexachrome swatch libraries or dedicated Hexachrome colour mode options, as the format became effectively obsolete for new work.

Modern Alternatives: Extended Gamut Printing

The concept behind Hexachrome — adding inks beyond CMYK to extend the printable gamut — did not disappear with the format. A newer generation of extended-gamut printing systems, sometimes called CMYK+ or ECG (Extended Colour Gamut) printing, uses similar principles. These systems typically add Orange, Green, and Violet inks to CMYK (CMYKOVG), providing an even broader gamut than Hexachrome. Vendors such as Epson (with their UltraChrome ink sets for wide-format printing) and commercial press manufacturers have developed proprietary ECG ink sets and workflows.

Unlike Hexachrome, modern ECG systems are primarily implemented at the press or printer level rather than in the design workflow: the designer works in a standard CMYK or Pantone-referenced colour space, and the RIP or press controller maps the colour to the expanded ink set automatically, using ICC profiles to manage the colour transformation. This makes ECG more transparent to the designer and reduces the barrier to adoption.

Hexachrome, PDF, and Spot Colour Workflows

For any PDF files created for Hexachrome output during its active era, the DeviceN colour space representation remains valid and readable by PDF-capable tools. However, reproducing Hexachrome output today requires access to compatible press hardware and RIP software, both of which are rare.

For jobs that require vivid oranges, greens, or violets and cannot achieve them within standard CMYK, the practical options today are: running the job with CMYK plus one or two specific Pantone spot colour plates for the critical brand colours; or working with a printer that offers a modern ECG press workflow. Both approaches are more widely supported than Hexachrome and can deliver the necessary colour fidelity for demanding print applications.