Colour Theory RGB & CMYK As a designer, it is essential to know when to use CMYK: cyan, magenta, yellow, and black (In the printing press days when plates were being used the black plate was typically call the “key” plate because it carried the important key information relating to the artistic detail.), and when to use RGB: red, green, blue colors on projects. A good rule of thumb is anything dealing with the web should always be in RGB and printed material should be in CMYK. RGB or CMYK?
CMYK
The color systems used by scientists and artists are entirely different. An artist will mix blue and yellow paint to get a shade of green; a scientist will mix green and red light to create yellow. The printed page in a magazine is yet another system.
The CMYK color model (process color, four color) is a subtractive color model, used in color printing, and is also used to describe the printing process itself. CMYK refers to the four inks used in some color printing: cyan, magenta, yellow, and key (black).
It’s important to define the two different kinds of color that we see in the world as the first step in understanding color systems. First, there’s the color you can touch, such as the skin of an apple or a painted wall. These colors are part of the surface of an object. Next, there’s the color you can’t touch, such as a beam of red light and the colors produced by your computer monitor. Colors generated by light are part of one color system. The tangible colors which are on the surface of objects or on the printed page are another color system.
RGB
The “K” in CMYK stands for key because in fourcolor printing, cyan, magenta, and yellow printing plates are carefully keyed, or aligned, with the key of the black key plate. The CMYK model works by partially or entirely masking colors on a lighter, usually white, background. The ink reduces the light that would otherwise be reflected. Such a model is called subtractive because inks “subtract” brightness from white.
CMYK
RGB The RGB color model is an additive color model in which red, green, and blue light are added together in various ways to reproduce a broad array of colors. The name of the model comes from the initials of the three additive primary colors, red, green, and blue. The main purpose of the RGB color model is for the sensing, representation, and display of images in electronic systems, such as televisions and computers, though it has also been used in conventional photography. Before the electronic age, the RGB color model already had a solid theory behind it, based in human perception of colors. 19
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