Blog | CMYK vs RGB

February 25, 2020


Have you ever received your yearbook and on inspection realized that some of the colours were not what you were expecting? This can happen if you don’t pay attention to what colour profile you are using when designing or choosing custom colours. Your colours look different on screen, because your computer displays in RGB (Red, Green and Blue) colour values and when your book is printed the CMYK (Cyan, Magenta, Yellow and Black) colour profile is used.

RGB uses an additive property to create colours by combining Red, Green and Blue light in varying degrees. When all three colours are combined to their full extent, the result is white. Combining all three colours to their lowest extent will result in black. RGB colour models are most often used in electronic devices as the screens tend to be darker. Combining red, green and blue light produces lighter colours, working in contrast to the dark screens.

CMYK is the colour profile in the printing industry standard. Colours are created using a subtractive process. This means when colours are added, more light is removed to create it. When Cyan, Magenta, and Yellow are combined, you will not achieve pure back, but rather a dark brown colour. Black is used to completely remove the light from the printed picture, which the eye sees as black. If you used 100% of all CMYK you would produce something called a rich or super black as opposed to the white you achieve with RGB. 

Two different colour profiles and two different light sources are at work here. RGB and CMYK colour profiles render differently depending on which medium they are being used for. RGB is best used for digital purposes because of the makeup of a digital monitor. A digital monitor is composed of tiny pixels, which are comprised of three light units, red, green and blue. When applying the RGB values to these pixels, you are setting the luminosity for each of the light units in the pixel, determining the colour of it. CMYK colour is best for printing because the colour white is already provided (as the piece of white paper.) The white acts as a base, while values of C, M, and Y are added creating different colours and shades. The more you add, the darker the colours get. Therefore, some colours can be printed but not displayed, and others can be displayed and not printed. This makes it nearly impossible to perfectly match the colours you see on the monitor to the printed page.

It is important to use CMYK when designing for print to ensure your desired colours translate correctly from the computer to the printed product. Friesens has calibrated all internal production equipment to yield consistent accurate colour. By selecting from the colours found in the Friesens Process Colour Press Guide, we can guarantee a match of the colours you want.