Color in Design: What Is CMYK and RGB
Before getting into the core of the topic, let’s see a few basics on what’s color and its perception. We could define color as the specific wave length of light reflected by the surface observed and captured by the human eye.
As Sir Isaac Newton discovered in the seventeenth century white light can be divided into several distinct colors ( by means of a ray of sunlight passing through a prism, after other strange experiments like passing needle into his eye, in an attempt to understand human sight.)
Surfaces will reflect certain wavelengths and retain others, thus the wavelength reflected is the light we see on the surface. The visible light has what is called three primary colors which are red, green and blue. They are called primary because combining these three colors you can create the whole hue spectrum.
And now, the important part, what does happen when you combine all the primary colors? In visible light if you mix them all together you get white light back, and that is the reason why visible light is known as an “Additive Color System.” If you were like me as a kid, and liked mixing paints and colors and making a real mess on your clothes with them your memories will bring a contradictory concept to what I just explained, when we mixed all the paints together we didn’t get white, to our despair our painted clothes didn’t get whiter, on the contrary they were more of a brownish, blackish color.
Why does pigment in paints go black instead of white? Because the pigment surface retains more light than it gives back, so as we add more and more pigment, less light is returned back thus getting a black reflection. For that reason pigments are known as “Subtractive Color Systems”
With all that said we can approach the two most known color systems in graphic design.
CMYK is a subtractive color system and for that reason adequate for printing as the pigments have that subtractive behaviour. While painters use the basic color wheel ( Red, Blue, Yellow ) as guide to mix colors, printing ink uses another set of primary colors: Cyan, Magenta, Yellow and blacK (CMYK). In theory cyan, magenta and yellow should be able to produce black but the mix isn’t rich enough to create a vivid and wide tonal range, for that reason black is added to the mix, forming what is known as “four-color process.” So from the designer point of view, you should use this color system when your project was intended for print, like letterheads, business cards or other stationary.
RGB is on the other hand an additive system, for that reason ideal for screen use. The combination with different percentages of Red, Green, Blue can generate the whole hue spectrum, being a 100% of each primary color the generation of white (with the same logic 0% of each generates black). Therefore RGB is a good system when you are working in web design projects, logos for web or screen use only and any other imagenery on screen.
There will be cases where as graphic designer you will need to provide solutions for both conditions (screen and print ) like a branding project. In those cases I provide my client in the style guide a palette with the CMYK and RGB values that match better the color chosen.