Colour Management
A guide to CMYK, RGB, and colour profiles for colour accuracy in professional print.
Colour Management
A guide to CMYK, RGB, and colour profiles for colour accuracy in professional print.
Colour Modes
RGB (Red, Green, Blue)
Use Cases:
- Screen display
- Web design
- Digital media
- Video
Characteristic: Light-based (additive). RGB combined produces white.
CMYK (Cyan, Magenta, Yellow, Key/Black)
Use Cases:
- Offset print
- Digital print
- Print shop jobs
Characteristic: Ink-based (subtractive). CMYK combined produces black.
RGB vs CMYK Comparison
| Characteristic | RGB | CMYK |
|---|---|---|
| Colour count | 16.7 million | ~1 million |
| Vibrancy | Very vibrant | Less vibrant |
| Neon colours | Possible | Difficult |
| Print compatibility | Conversion required | Direct |
Colour Shift
Transitioning from RGB to Print
Some colours are lost when converting from RGB to CMYK:
| RGB Colour | CMYK Equivalent | Difference |
|---|---|---|
| Neon Green | Dark Green | Noticeable |
| Bright Blue | Flat Blue | Moderate |
| Orange | Similar | Minor |
Recommendation: Start your design in CMYK mode if possible. NowToPrint reports RGB risk; the actual colour conversion is performed downstream by the RIP/DFE.
Colour Profiles (ICC)
Common Profiles
| Profile | Usage |
|---|---|
| ISO Coated v2 | European coated paper |
| FOGRA39 | European standard |
| US Web Coated (SWOP) | US standard |
| Japan Color 2001 | Japanese standard |
Profile Selection
Recommended for NowToPrint:
CMYK: ISO Coated v2 (ECI)Colour Consistency
Monitor Calibration
Calibrate your monitor for accurate colour display:
- Use a professional calibrator
- Set brightness to ~120 cd/m²
- Colour temperature: 6500K
Soft Proofing
For a print preview:
- In your design software: View → Proof Colors
- Select the CMYK profile
- Review the colour differences
Problematic Colours
Colours That Are Difficult to Print
| Colour | Problem | Solution |
|---|---|---|
| Neon/Fluorescent | Not available in CMYK | Spot colour or alternative |
| Metallic | Requires special ink | Metallic paper + CMYK |
| Very dark blue | Converts to black | Lighten the value |
Total Ink Limit
The CMYK total (C+M+Y+K) must not exceed the specified limit:
Coated paper: Maximum 300%
Newsprint: Maximum 240%Example:
- C:100 + M:100 + Y:100 + K:100 = 400% — Too high
- C:80 + M:80 + Y:80 + K:50 = 290% — Acceptable
Spot Colours
Pantone (PMS)
Specially formulated inks:
- Consistent colour (the same everywhere)
- Wide colour gamut
- Metallic and neon options available
- Additional cost
When to Use Them
- Logo printing (brand consistency)
- Corporate colours
- Special effects (gold, silver)
Colour Verification
Preview
The print preview in NowToPrint simulates CMYK output:
- Appearance close to the final print
- Identifies potential issues
Colour Bar
In professional print, colour bars are added alongside crop marks for colour verification.
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