Short answer
Process colour builds every colour from dots of cyan, magenta, yellow and black; a spot colour is a separate ink mixed to one target and printed as its own plate. Use a spot colour when a brand colour lies outside the CMYK gamut, must be consistent across runs and suppliers, or is a special (metallic, fluorescent, pastel) process inks cannot make. Extended-gamut printing with orange, green and violet can reach many former spot colours with a fixed ink set.
A process colour is a recipe of four inks at different dot percentages. It depends on every variable of the press — density of four inks, dot gain in each, registration — so its colour moves as the run drifts, and its gamut is limited to what the four inks can reach on that paper. A spot colour is ink mixed in advance, usually from a base-ink formula in a colour-matching system, and printed as a solid or tint from its own plate. Its colour depends on one ink's film thickness and the paper, which makes it easier to hold and able to reach colours outside the process gamut.
Each spot colour adds a plate, a press unit, washing up and ink-mixing time, so it has to earn its place. It does when the colour is a brand essential outside the process gamut (strong oranges, bright greens, deep violets, reflex blues); when it must match across different printers, papers and years; when it appears as a large flat area where process-dot mottle would show; and when the effect is physically impossible in CMYK — metallic, fluorescent, opaque white on dark board, or very clean pastels. For a colour well inside the process gamut on short runs, a controlled CMYK build is usually cheaper and adequate.
Commercial matching systems such as Pantone publish swatch books of numbered colours, each with an ink formula, printed on coated and uncoated papers because the same ink looks different on each. They are proprietary systems and their colour data are not reproduced here. Two practical points: the swatch book is itself a print and fades and varies by edition, so critical matches use a measured CIELAB target with a tolerance; and the CMYK 'equivalents' such systems publish are approximations for one printing condition, often visibly different from the spot ink.
Extended-gamut printing adds orange, green and violet to CMYK and prints every job with the same seven inks. The added primaries push the gamut out where CMYK is weakest, so many spot colours can be simulated without changing inks between jobs — valuable in packaging, where swapping spot inks on a press is costly. Characterisation data for seven-colour conditions are now registered with the ICC alongside CMYK ones. The trade-offs are separation complexity (seven channels need special profiling software), tighter press control, and simulations that are close but not identical to a mixed spot ink, especially for very clean or special colours.
Why: The swatch was converted to process in the export or the file used a process 'equivalent'.
Fix: Check separations before sending: the spot colour should appear on its own plate.
Why: Different swatch-book editions, paper or fading; the reference itself varies.
Fix: Specify a measured CIELAB target with a ΔE00 tolerance and the measurement condition.
Why: The spot colour lies outside the process gamut; the published CMYK equivalent is the closest approximation.
Fix: Approve a separate process version of the brand colour, soft-proofed for the actual condition.
Each statement is labelled by kind — established fact, a standard’s requirement, observed market data, a convention, or Colourwise’s own interpretation or analysis — with the strength of the evidence behind it.
StandardStrong evidence
ISO 12647-2:2013 allows additional spot colours in offset printing but makes no provisions for their tolerances, while ISO 12647-7:2016 sets an optional maximum of 2.5 ΔE00 for spot-colour solids on contract proofs.
Source: ISO 12647-2:2013 Graphic technology — Process control … — Part 2: Offset lithographic processes; ISO 12647-7:2016 … — Part 7: Proofing processes working directly from digital data
FactStrong evidence
A seven-colour (CMYK plus orange, green and violet) printing condition on premium coated paper, measured to M1, is registered in the ICC's characterisation data registry.
Colourwise interpretationModerate evidence
A spot colour is easier to hold consistent than a process build of the same colour because its appearance depends mainly on one ink film rather than on the density and dot gain of up to four inks.
Based on: Follows from how process colours are built from four halftoned inks each with its own density and TVI variation, compared with a single premixed ink.
Reviewed 29 September 2026. Colourwise summarises its sources in its own words and does not reproduce standards text or proprietary colour data. Spotted an error? Tell us.