Colors in Graphics

Understanding Colors

There are two basic types of color system.
1: RGB colors (Red, Green, Blue)
RGB colors are also know as "Additive colors" & "Primary colors"

2: CMYK colors (Cyan, Magenta, Yellow, Black)
CMYK colors are also known as "Subtractive Colors" & "Secondary colors"

If we are going to design for TV or Web we'll use "RGB" color system.
and if we are going to design for Print media then use "CMYK" color system.

Light:
In order to understand color we need a brief overview of light. Without light , there would b no color, and hence no RGB world.

Primary colors can be arrange in circle, commonly referred to as a "Color Wheel". Red, Green, Blue (RGB)  from a triangle on the color wheel. In between the primary colors are the secondary colors, Cyan, Magenta, Yellow, Black (CMYK), which form another triangle.

Visible Light

The wavelengths our eye can detect is only a small portion of the electromagnetic energy spectrum. We called this, "The visible light spectrum". At one end of the visible spectrum are the short wave lengths of light we perceive as blue. At the other end of the visible spectrum are the longer wave lengths of light we perceive as red. All the other colors we can see in nature are found somewhere along the spectrum between blue and red.

Non - Visible Light

Beyond the limits at each end of the visible spectrum are the short wave lengths of the ultraviolet light and X-rays and the long wave lengths of infrared radiation and radio waves, which are non visible to human eye.

Primary Colors

If the visible portion of the light spectrum is divided into thirds, the predominant colors are red, green and blue. These three colors are considered as "Primary colors" of the visible light spectrum.

Additive Color System (RGB)

The additive color system involves light emitted directly from a source, before an object reflects the light. The additive reproduction process mixes various amounts of red, green and blue light to produce other colors. Combining one of these additive primary colors with another produces the additive secondary colors cyan, magenta, yellow. Combining all three primary colors produces white.

Uses of Additive color system
Televisions and computer monitors create color using the primary colors of the light. Each pixel on a monitor screen starts out as black. when the red, green and blue phosphors of a pixel are illuminated simultaneously, that pixel become white.

Subtractive Color System (CMYK)
Photographs, magazines, and other object of nature such as an apple, create color subtracting or absorbing certain wavelengths of color while reflecting other wavelengths back to the viewer. This phenomenon is called subtractive color.
                                    A red apple is a good example of subtractive color, the apple really has no color, it has no light energy of its own. It merely reflects the wavelengths of white light that cause us to see red and absorbs most of the other wavelengths which evokes the sensation of red. The viewer (or detector) can be the human eye, film in a camera or a light sensing instrument.

Printing Process

Color paintings, color photography, and all color printing processes use the subtractive process to reproduce color. In these cases, the reflective subtract is canvas (paintings) or paper (photographs, prints) which is usually white.

The Purpose of "K" in in CMYK
Printing presses use use color inks that act as filter and subtract portions of the white light striking the image on paper to produce other colors. Printing inks are transparent, which allows light to pass through to and reflect of the paper base. It is the paper that reflects any unabsorbed light back to the viewer. The offset printing process use cyan, magenta and yellow (CMY) process color inks and a fourth ink, black. The black printing ink is designed "K" to avoid confusion with "B" for blue.
Over printing one transparent printing ink with another produces the subtractive secondary colors, red, green, blue.