When designing for print, the colour mode you use is extremely important: whilst computers use the RGB colour model to display graphics, printers most commonly use a different model called CMYK. If you have your graphics software configured to the wrong colour mode, what is displayed on your computer may not look the same as what is printed. The result may look bad and a full reprint could make this a very costly error. It’s important to know the uses and differences between the two colour modes to optimise the quality of your printed media.
RGB stands for Red, Green and Blue. The RGB colour model combines these basic colours to make almost any colour imaginable. For example, combining red and green would produce yellow. Combing all three colours produces white. The colour produced depends on the amount of red, green and blue added. Computer monitors, and LCD and LED televisions usually use RGB colour mode (though, the colour shown on screen may vary between screens due to the hardware limitations of both the screen and the actual computer) and whilst some new printers do, a lot of printers use CMYK colouring so you need to be careful when going form PC to printer.
CMYK stands for Cyan, Yellow, Magenta and Key (usually black). Whilst combing RGB colours is additive (meaning combing all them will produce a bright colour – white if added equally), combining CMYK is subtractive, meaning the more colours you mix, the darker the colour will be. The main idea of CMYK is to combine CMY to obtain the right colours, and then add black to get the correct shade of the colours. For example, if you combine magenta and yellow, it will produce a bright red colour. Adding black to this could produce brick red. As stated above, CMYK is only really used in some printers, so you should be sure of the colouring mode of your printer before printing straight away.
Going from RGB to CMYK
If not properly converted, the colours from a program such as photoshop can end up looking much different to the printed colours. For example, blues usually look more vibrant in RGB than they do with CMYK. Therefore, you should always make sure you can convert the colour properly from RGB to CMYK.
Due to the colouring freedom RGB provides, it is usually easier to produce an image in RGB and then convert to CMYK before printing. However, this can depend on your design. If your design has a lot of dark grey/black in it, printing using RGB would use up a lot of each colour of ink. However, with CMYK, not much of CMY would be used, since all the darkness would come from the black ink cartridge. Therefore, this would be cheaper. If your design is mostly bright colours, it may not be necessary to convert it from RGB to CMYK at all.
If you do choose to convert, programs like photoshop allow you to fine-tune your conversion process. You can preview what your image would look like after their standard RGB-CMYK conversion, and the decide whether or not to add more cyan or magenta etc. However, there is always the option to create your piece using CMYK colours from the very start. By doing this, it is very likely that the image printed will be extremely similar if not the exact same as the image produced on screen.
When printing with CMYK, it can be difficult deciding on what shade of black to use, and what would be most cost efficient. Rich black doesn’t just use only the black ink; it uses a mixture of black and cyan, magenta and yellow. A typical rich black mixture could be 100% black, and 50% of the other three inks. Figuring out the best combination for your print-out could be key in making it stand out.
And there you have it! Colour is everything on printed media – whether it be brochures or mailshots. To ensure your colours stand out, you need to familiarise yourself with RGB and CMYK colouring.