The three colour systems
| System | How it makes colour | Used for |
|---|---|---|
| RGB | Red, green and blue light added together | Screens, websites, phone photos, social media |
| CMYK | Cyan, magenta, yellow and black ink layered on paper | Full-colour printing of photos and designs |
| Pantone (PMS) | Pre-mixed spot ink matched to a numbered swatch | Exact brand colours, logos, one- and two-colour jobs |
Why colours shift
Screens emit light and can show very bright, saturated colours (electric blues, neon greens) that ink on paper simply can't reproduce. When an RGB file is converted to CMYK those colours become slightly duller. Converting your file to CMYK yourself lets you see and adjust the change before printing rather than after. Your monitor's brightness also matters; a printed proof is the best way to judge colour.
When to use Pantone
If your logo must match exactly from job to job (signage, stationery, packaging), specify the Pantone number. Offset jobs can print the spot ink directly; on digital presses we match it as closely as possible in CMYK. Use the coated (C) or uncoated (U) swatch that matches your paper.
Getting blues and purples right in CMYK
Blues and purples are both built mostly from cyan and magenta, so the balance between those two inks decides which one you get. On press, that balance moves a little: ink density varies from sheet to sheet, different papers absorb ink differently, and dot gain (halftone dots spreading as ink soaks into paper) tends to make colours print heavier than they look on screen. Magenta is a strong, warm ink, so even a small extra push toward it is easy to see.
- Blues with too much magenta shift purple. C100 M100 looks like a royal blue on many screens but often prints as a violet or purple.
- Purples with too little gap between cyan and magenta shift blue. C90 M100 is close to equal, so with a little variation it can read as a dark blue rather than a purple.
Rules of thumb
These are general guidelines, not absolutes; the exact result depends on the press, paper and the rest of your design.
- For a true blue, keep magenta well below cyan, commonly about 30 points lower. For example, use C100 M70 rather than C100 M100.
- For a purple, keep a clear gap with magenta higher than cyan, roughly 20–30 points or more. For example, use C60 M100 rather than C90 M100.
- Watch RGB-to-CMYK conversions. Bright RGB blues such as pure blue (R0 G0 B255) can’t be printed as-is and often convert with magenta close to cyan (around C90 M75 or higher), which prints purple. Check converted blues and bring the magenta down.
- Add black, not more magenta, to deepen a blue. A navy like C100 M70 Y0 K30 stays blue; pushing magenta up to darken it pulls it toward purple.
| Goal | Risky build | Safer starting build | Why |
|---|---|---|---|
| Bright / royal blue | C100 M100 | C100 M70 | Magenta well below cyan keeps it blue |
| Navy blue | C100 M100 K40 | C100 M70 K30–40 | Use black for depth instead of magenta |
| Sky / light blue | C60 M40 | C60 M15 | Low magenta keeps light blues clean |
| Royal purple | C90 M100 | C60 M100 | Clear gap with magenta higher |
| Violet / blue-purple | C100 M95 | C75 M100 | Keep magenta clearly ahead |
| Lavender | C30 M30 | C25 M45 | Even light tints need the magenta lead |
Tips for colour-critical blues and purples
- Request a hard (printed) proof on your actual paper when the colour really matters; screens can’t show how the inks will balance. See printed proofs.
- Consider Pantone for brand blues and purples. A spot colour is pre-mixed, so it doesn’t depend on a cyan/magenta balance, and many vivid blues and purples sit outside the CMYK range altogether.
- Tell us which colour must be right, and our prepress team can check your builds before printing.
Black: rich vs plain
- Small text and thin lines: use 100% K (black only) so they stay crisp and don't show colour fringes.
- Large black areas: use a rich black such as C60 M40 Y40 K100 for a deep, even black.
- Avoid 4-colour black (100/100/100/100): too much ink can smear and dry poorly. Keep total ink under about 300%.
Frequently asked questions
- Should I send RGB or CMYK files?
- CMYK is best for print. If you send RGB we convert it, but bright colours can look duller; converting yourself lets you check first.
- Why did my blue print purple?
- Usually because the blue had too much magenta for its cyan (for example C100 M100, or a bright RGB blue converted to CMYK). Press and paper variation and dot gain push it further toward purple. As a general guideline, keep magenta about 30 points below cyan for a true blue, such as C100 M70, and request a printed proof for colour-critical work.
- Can you match my Pantone colour?
- Yes. Give us the Pantone number. We print spot colours on offset jobs and match them closely on digital jobs, and we can provide a proof.
Related services
Helpful customer tools
- PreFlight Checker (flags RGB images) (available to customers with a free account)
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