Colour Modes – RGB and CMYK

We often hear about colour modes and what we should use when creating artwork for different purposes. Even more so, when creating a new document we are asked to select a colour mode or to accept the the default, (it’s too easy to just press ‘OK’ and move on!)

Creating a new environment for our file is arguably the most important moment in the life of that file; the correct selection of colour mode will make a big impact on our final result.

Colour Modes - RGB and CMYK Image 1


The Red Green Blue Colour Mode (RGB) is an additive colour mode in which Red, Green and Blue are added together in various configurations to display a spectrum of colour. On our computer screens we see RGB added to a white light source to reflect colour at us. As well as on computer screens, RGB is the colour mode used on Digital Cameras, Scanners, TV’s and phones. In fact, it is the colour mode utilised on all digital devices.

Colour Modes - RGB and CMYK: RGB Colour Mode.

Being a colour mode on a digital device means we can specify RGB colour with great accuracy. It is worth noting that not all devices are calibrated to provide the same impression of a particular colour, nor do our eyes see it the same.

RGB specifies the Red, Green and Blue colour channels individually as values between 0 and 255. We can pinpoint a colour by providing a number for each channel.


Colour Modes - RGB and CMYK: RGB Example


RGB has the ability to display lots of colours. If you think about all the colours your eyes can see as the visible spectrum, under that sits all of the colours an RGB screen can display and we can see as a light source of colour coming towards us. We then need to look at CMYK and what source of colour mode that is and when it is used.

Cyan, Magenta, Yellow and Black, CMYK is used in printing. It is a subtractive colour mode, meaning it uses the white space around it (on fabric or paper) and an overlay of combinations to create a full colour library.

CMYK is directly connected to the physical world of inks. It is measured in percentage from placing down 0% – 100% of any of the Cyan, Magenta, Yellow and Black inks to create colour. The job of a printer is to transfer a digital artwork into a realistic interpretation using inks laid down onto a substrate, in a combination of tiny little drops.

Colour Modes - RGB and CMYK: CMYK Example

Consider that inks are being used onto a tactile surface to create an image. Does this mean CMYK can produce more or less colours then RGB? If you answered less, you are correct.

RGB has the light source and can produce dynamic and full-bodied colour, but not as much as our eye can see. CMYK is limited to the ability to lay down ink to produce a likeness of a colour our eye desires to see. This sizing up of colour against different modes is referred to as Gamut.


Of course there are always exceptions, with the development of new technology and inks we can now offer specialisation in many different colour reproductions in print.

So what do we create our files as? RGB of course! Why?

  • RGB has the biggest Gamut. Don’t limit yourself to less!
  • It is the role of the printer to create the interpretation of colour and translate it into inks.
  • If you create a CMYK file you will be telling the printer what percentage of inks to lie down to create a colour. Do you know what 80% of yellow will look like on a particular printer?