Choosing the Right Colour Mode for Print.

If you’ve ever sent a design to print only to find the colours look completely different from what you saw on screen, you’ve likely encountered the fundamental difference between RGB and CMYK colour modes. Understanding these two colour systems is essential for ensuring your printed materials match your expectations. Let’s explore what RGB and CMYK mean, why they produce different results, and how to work with them effectively.

What is CMYK?

CMYK stands for Cyan, Magenta, Yellow, and Key (black). These are the four ink colours used in most commercial printing processes. Unlike RGB, CMYK works through subtractive colour mixing. Instead of adding light, you’re adding ink to white paper, and each layer of ink absorbs (or subtracts) certain wavelengths of light.

When light hits printed paper, the paper and inks absorb some wavelengths and reflect others back to your eyes. Cyan ink absorbs red light, magenta absorbs green light, and yellow absorbs blue light. By combining these inks in different amounts, printers can create a wide range of colours. The black ink (K) is added because mixing cyan, magenta, and yellow together produces a muddy brown rather than a true black, and having dedicated black ink also makes printing more efficient and economical.

Imagine painting with watercolours on white paper. Each layer of paint you add makes the overall result darker because you’re blocking more light from reflecting off the white paper beneath. That’s essentially how CMYK printing works, which is why it’s called subtractive colour mixing.

What is RGB?

RGB stands for Red, Green, and Blue, the three colours of light that combine to create every colour you see on screens. Your computer monitor, phone, tablet, and television all use RGB to display images. This system works through additive colour mixing, where colours are created by adding light together. When you combine red, green, and blue light at full intensity, you get white. When there’s no light at all, you get black.

Think of RGB like shining three coloured torches onto a white surface. Where the beams overlap, they create new colours. Red and green together make yellow, blue and green create cyan, and red and blue produce magenta. Because RGB uses light emission, it can create incredibly bright, vivid colours with a wide range of intensity.

RGB is perfect for anything displayed on a screen: websites, digital presentations, social media graphics, and video content. The colours can be brilliant and saturated because screens emit their own light. However, this is precisely why RGB doesn’t work well for print.

Why Colours Look Different Between Screen & Print.

Here’s the crucial point: RGB can produce colours that CMYK simply cannot replicate, and this is the root cause of those disappointing colour shifts when printing. The range of colours a system can reproduce is called its gamut, and RGB has a significantly wider gamut than CMYK.

Those vibrant electric blues, brilliant hot pinks, and neon greens that look stunning on screen often fall outside CMYK’s capabilities. When you convert an RGB image to CMYK for printing, these out of gamut colours must be shifted to the nearest colour that CMYK can actually produce. This usually means colours become less saturated, less bright, and sometimes shift in hue.

Additionally, screens emit light in a dark room and can appear incredibly bright, whilst printed materials rely on ambient light reflecting off paper. Even if you could perfectly match a colour between screen and print, the print version would never look as luminous because it’s reflecting light rather than generating it.

When to Use RGB.

Use RGB for anything that will only be viewed on screens. This includes website graphics, digital advertisements, social media content, email newsletters, PowerPoint presentations, and any digital photography or artwork intended for screen display. Working in RGB gives you access to the full range of vibrant colours that screens can display.

If you’re creating content that might be used both digitally and in print, you’ll need to manage both colour modes. Many designers keep a master RGB version for digital use and create a separate CMYK version specifically for print, adjusting colours as needed to achieve the best possible print results.

When to Use CMYK.

For anything destined for commercial printing, you should work in CMYK from the start or convert to CMYK before finalising your design. This includes brochures, business cards, posters, magazines, packaging, and any other printed materials. Working in CMYK from the beginning allows you to see how colours will actually print and make informed design decisions.

Converting to CMYK early in your design process prevents nasty surprises when you send files to print. You’ll immediately see which colours fall outside the printable range and can adjust your palette accordingly. Waiting until the last moment to convert often means discovering that your carefully chosen colour scheme doesn’t translate well to print.

The Conversion Challenge.

Converting from RGB to CMYK isn’t just a simple file format change. It requires careful attention and often manual adjustment. Design software like Adobe Photoshop, Illustrator, and InDesign can perform automatic conversions, but the results aren’t always ideal. Automatic conversion uses algorithms to shift out of gamut colours, but these algorithms don’t know your design intent or which colours are most important to preserve.

The best approach is to convert to CMYK and then carefully review your design, paying special attention to areas with bright, saturated colours. You may need to manually adjust colours to achieve results closer to your original vision. Sometimes this means choosing slightly different colours that print better, or adjusting the balance of your entire colour scheme to work within CMYK’s limitations.

Certain colours are particularly problematic. Bright oranges often shift towards red, vivid purples can become muddy, and brilliant blues tend to darken. If your brand colours fall into these troublesome ranges, it’s worth creating specific CMYK formulas for them and testing printed samples to ensure consistency.

Practical Tips for Managing Colour Modes.

Always ask yourself where your final design will be used before you start working. If it’s destined for print, begin in CMYK. If it’s for digital use only, work in RGB. For projects that need both, create your design in RGB to maintain flexibility, then convert a copy to CMYK for print and adjust as needed.

When sourcing images from stock libraries or photographers, check whether you’re receiving RGB or CMYK files. Most digital photographs are RGB, which is fine, but you’ll need to convert them properly for print. If you’re scanning materials, your scanner settings should match your final use: RGB for screen, CMYK for print.

Educate clients and colleagues about the differences between RGB and CMYK early in projects. Managing expectations from the start prevents disappointment when vibrant screen colours translate to more subdued print colours. Consider creating printed colour samples of key brand colours so everyone understands how they’ll actually appear in print.

The Bottom Line.

Understanding RGB and CMYK isn’t just technical knowledge for designers. It’s essential for anyone involved in creating printed materials. The fundamental difference between light based screen colours and ink based print colours means what you see on screen will rarely match exactly what comes off the press.

By working in the appropriate colour mode from the start, converting carefully, and setting realistic expectations about colour reproduction, you can ensure your printed materials look their best. Yes, some colours will shift from screen to print, but understanding why this happens and planning for it means you’ll achieve professional results that effectively represent your brand.

Questions About Colour for Your Print Project?

Colour management can be complex, and every project has unique requirements. If you’re unsure about colour modes, concerned about how your colours will print, or need advice on achieving the best results for your specific project, we’re here to help. Getting colour right from the start saves time, money, and ensures you’re happy with your finished printed materials.