Short answer
Because a printed blue is made by overprinting cyan and magenta, and both inks absorb more of the blue light they are meant to pass than an ideal filter would. The result is a darker, greyer, often slightly violet blue with well under half the chroma of an sRGB screen blue. Oranges, bright greens and violets suffer similarly; how much depends on paper and ink set, and coated paper loses least.
There is no blue ink in four-colour printing. Blue appears where cyan (which absorbs red) and magenta (which absorbs green) overlap, leaving mainly blue light to reflect from the paper. In an ideal world both inks would be perfectly transparent to blue. Real process cyan and magenta each absorb a share of blue as well — magenta in particular has an unwanted blue absorption — so the light surviving both layers is dimmer and less pure. The overprint is dark (L* about 25 on coated offset) and only moderately chromatic, and small shifts in either ink's density swing it between violet and teal.
Using the published characterisation data, the table on this page compares each sRGB primary and secondary with the corresponding press solid or overprint. The blue gap is the widest: roughly 134 units of CIELAB chroma on screen against about 52 on premium coated paper and about 33 on uncoated. Green and red also shrink, magenta and yellow less so. Cyan goes the other way — press cyan is more chromatic than sRGB cyan — which is why a strong printed turquoise can look disappointing in an sRGB preview but fine on paper.
Screen blues near the sRGB primary are both very dark and very saturated, a region no mixture of cyan and magenta on white paper reaches. When a conversion has to bring such a colour into gamut, it can keep the hue and drop the chroma, keep the lightness and drop the chroma, or bend the hue towards violet or cyan. Colour-managed conversions usually keep hue approximately, but the blue region of CIELAB itself is not perceptually uniform, so a mathematically 'same hue' mapping can look purple. That is a known weakness of CIELAB that CIEDE2000 corrects for differences but that profile makers must handle separately in their gamut mapping.
Print on coated stock: the gap between coated and uncoated blue is itself large. Keep the blue as a controlled CMYK build chosen from the soft proof rather than letting an intent pick one. If the colour is a brand essential, use a spot ink mixed to the target, or an extended-gamut process (CMYK plus orange, green and violet) whose violet channel reaches further into the blue-violet region. For images, perceptual rendering keeps gradations in blue skies and water instead of flattening them into one clipped value.
| Colour | sRGB (screen) chroma | Coated offset FOGRA51 chroma | Uncoated offset FOGRA52 chroma |
|---|---|---|---|
| Blue | 133.8 | 51.9 | 33.4 |
| Green | 119.8 | 70.3 | 42.9 |
| Red | 104.6 | 83.1 | 61.5 |
| Magenta | 115.5 | 75.5 | 60.2 |
| Yellow | 96.9 | 92.5 | 72.4 |
| Cyan | 50.1 | 63.1 | 53.1 |
Why: The out-of-gamut blue was mapped along a CIELAB hue line that looks violet, or magenta ran heavy on press.
Fix: Pick a CMYK blue build in the soft proof with less magenta relative to cyan, and specify its tolerance.
Why: Relative colorimetric clipping mapped many distinct out-of-gamut blues to the same edge colour.
Fix: Use perceptual intent for photographs with large out-of-gamut areas.
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.
FactStrong evidence
In the FOGRA51 coated offset data the blue (cyan plus magenta) overprint is L* 24.74, a* 21.12, b* −47.45, and in the FOGRA52 uncoated data it is L* 38.47, a* 9.76, b* −31.96.
Source: FOGRA51 characterization data (premium coated offset, ISO 12647-2:2013); FOGRA52 characterization data (wood-free uncoated offset, ISO 12647-2:2013)
Colourwise analysisStrong evidence
Computed from the published data, press cyan on coated paper (chroma about 63) is more chromatic than the sRGB cyan secondary (about 50), while every other sRGB primary and secondary exceeds its coated-offset counterpart.
Based on: CIELAB chroma of the sRGB values computed with Colourwise's colour library (D65 white) against FOGRA51 solids and overprints (D50); see the table.
Caveat: Chroma relative to each system's own white; no chromatic adaptation is applied, so treat differences of a few units as approximate.
Source: FOGRA51 characterization data (premium coated offset, ISO 12647-2:2013); International Electrotechnical Commission (IEC) webstore and catalogue
FactStrong evidence
Perceived hue lines in CIELAB bend in the blue region, which is why CIEDE2000 includes a term specifically for blue colour differences.
Source: The development of the CIE 2000 colour-difference formula: CIEDE2000; Precise Color Communication
FactStrong evidence
Extended-gamut printing conditions using cyan, magenta, yellow and black plus orange, green and violet are registered with the ICC in the same way as four-colour conditions.
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.