What Is the CMYK Colour Gamut?

What is a colour gamut?

A colour gamut is the range of colours a device can show or a process can print. Every screen and every printing process has its own. A colour outside that range can’t be produced, however the file is set up.

Screens make colour from red, green and blue light (RGB). Full colour cards are printed with cyan, magenta, yellow and black ink (CMYK). The CMYK range is the smaller of the two, so some colours you can see on screen have no printable match.

A colour outside the line is called out of gamut. When the file is converted to CMYK, it moves to the nearest colour the inks can make, and that’s usually duller. Adobe’s Photoshop help says Photoshop remaps out-of-gamut colours automatically when you convert from RGB to CMYK, and that some colour detail or vibrancy may be lost. This is a limit of CMYK printing in general, not of one printer or one machine.

Why is the RGB gamut wider?

The RGB gamut is wider overall, because a screen gives out light while a card can only reflect the light its inks don’t absorb. That’s why a screen colour can seem to glow and a printed one can’t.

Not every screen covers the same range either. Newer phones and some monitors show more vivid colours than older screens, and print can’t reach the most vivid of them. Going the other way, Adobe says its Adobe RGB space can represent more printable colours than sRGB, the standard screen space, particularly in cyans and blues. That’s why real gamuts never nest as tidily as our drawing.

Our guide to CMYK vs RGB shows how to convert a file, step by step. Artwork from an AI image tool is always RGB, and why AI artwork needs converting shows what that does to it.

Which colours go duller in CMYK?

The most saturated colours go duller the most: neon and bright greens, electric blues, vivid oranges, hot pinks and strong purples. Darker and more muted colours usually convert closely.

Two colours show how far the numbers can move. The exact mix depends on the conversion profile used.

Yellow is a true gamut problem: even at full strength, yellow ink can’t match the yellow light of a screen, and the conversion takes it further away, to 79% yellow with a little cyan and magenta in it. Black is a different problem. K100 is printable, but the conversion gives you a mix of all four inks, which prints a dark, muddy brown. Our guide to designing a black plastic card shows how to set it.

Neon and glow effects are the hardest case, because fluorescent colours can’t be made from the four inks at all. Brand colours picked on screen can catch you out too: see Pantone colours and plastic cards if yours is a Pantone number.

How do I check my artwork for out-of-gamut colours?

Use your design software’s gamut warning while the file is still in RGB. Once it’s converted, every colour has been moved into gamut, so there’s nothing left to flag. Better still, set your document to CMYK from the start if you can, so you’re choosing from colours the inks can print. Our membership card template is already in CMYK.

• Photoshop, the whole picture. Choose View > Proof Setup and pick a CMYK profile, then choose View > Gamut Warning. Out-of-gamut colours show in grey. Any standard CMYK profile is fine for this.
• Photoshop, one colour. An alert triangle appears in the Color Picker or Color panel when a colour can’t be printed. Select it to see the closest CMYK equivalent.
• Illustrator. Select the object. If its colour is out of gamut, an alert triangle shows in the Color panel or Color Picker. Click it to move to the closest CMYK equivalent.
• Canva and browser tools. Most don’t give you this control. Canva’s paid plans can download a CMYK PDF, and our Canva guide shows the settings. Choose plain, less vivid colours if you can’t check them.

Treat the warning as a guide. Print profiles are measured on paper, and our standard full colour cards are plastic, with clear PVC over the print. The warning tells you which colours are at risk, not how the card will look.

A quick check before you send your file

Our free artwork check is technical: bleed, resolution, colour mode and file set-up. If you can only produce an RGB file, send that: the check will flag the colour mode, and we can convert it for £10 +vat. Whether a colour looks right is your call, so look at the CMYK values of your main colours after converting. Our guide to print-ready artwork covers the rest of what a file needs.

How do you get bright colours in CMYK?

Choose the CMYK numbers yourself rather than leaving them to a conversion, and use as few inks as you can. The more ink on the card, the darker the result, so leave black out of a bright colour. Your CMYK values are printed as they are, whatever colour profile is attached.

• Start from the chart. Our CMYK colour guide shows swatches with their percentages, as a rough guide, because it’s still on a screen. The colour wheel helps you pick colours that go together.
• Keep black out of bright colours. Black ink darkens a colour.
• Choose High Gloss. It makes colours look deeper and more vibrant, and it’s included. Premium Matt softens and dulls them a little.
• Use contrast. Our own design tip: a bright colour looks brighter beside a dark one.
• Or ask us to do it. Our designers convert AI artwork and enhance its colours for £10 +vat, or £29 +vat if the work is more extensive, and we tell you which before we start. Our design service is £29 +vat if you’d rather we built the artwork.

When is foil or a metallic card the better route?

When you want a metallic shine or a flat, solid colour rather than a mix of dots. Metallic colours can’t be made from the four inks, but foil isn’t CMYK at all: each foil is its own colour, from a fixed range of 42 metallic and pigment foils. It suits logos and clean type, not photographs or gradients.

Hot foil cards are quoted individually from your design. On a hot foil proof, the colours are a guide only, and the same foil can look different on a frosted, white, satin black or metallic card. If in doubt, email sales@cpcards.co.uk to ask about a sample colour being posted to you for approval.

Will the proof show me how bright my colours will print?

The free email proof won’t, and it isn’t meant to. Every full colour order comes with a free photorealistic proof by email, so you can check the layout and wording. The colours on the proof are a guide only, because every screen shows colour differently. If a colour has to be right, add a postal proof.

A postal proof is a few real cards posted to you. It’s optional, costs £65 +vat and takes around 5 working days, and it’s for full colour cards. Most customers don’t add one, but it’s the way to judge a bright colour on a real card, in your own light.

Our terms and conditions cover this too: colours on your monitor will most probably not match the printed colour (8.1), printed colours and their density will vary (8.2), and RGB or Pantone colours are converted to CMYK, so they will change (8.5). Our page on colour profiles explains why no screen can show a plastic card.