DIGITAL IMAGE COLOR SCHEMES (Ref: Adobe Photoshop)

RGB Model	(Red, Green, Blue) - Describes the content of each of three primary colors Red, Green, and Blue, the same as the cones in the retina of the human eye.
	The RGB model assigns intensity values of each primary color light generated and to be transmitted in combination (additive) to our eyes within the dot-area of each pixel (dot) of a color image, each ranging from 0 (or 00 - hex zero) to 255 (or ff - hex full intensity). For example, the binary (hexadecimal) map above shows the contents of an image of a red solid colored square. Each pixel then is described by three numbers: the R value is 255 (ff - full RED intensity), and the green and blue are both zero (00 - GREEN and BLUE turned off). This shows for each pixel described as repeated sequences of 24 (8R + 8G + 8B) bits in hex containing "ff 00 00", i.e. Red (full), Green (none), and Blue (none). When the values of all three components are zero (00 00 00) the result is black (all ZERO, darkness). When the three are non-zero but equal, the result is some shade of neutral gray. When the value of all components is 255 (ff ff ff), the result is ALL colors ON, looking as full white. NOTE: If you use a strong magnifying glass on the LCD screen of your computer, digital television or cell telephone screen with a color display, you should be able to see the individual trios of RGB colored "pixel" rectangles.

Hue - Is the color reflected from or transmitted through an object. It is measured as a location on the standard color wheel, expressed as a degree between 0° and 360°. In common use, hue is identified by the name of the color such as red, orange, or green.

Saturation - Sometimes called chroma, is the strength or purity of the color. Saturation represents the amount of gray in proportion to the hue, measured as a percentage from 0% (gray) to 100% (fully saturated). On the standard color wheel, saturation increases from the center to the edge.

Brightness - is the relative lightness or darkness of the color, usually measured as a percentage from 0% (black) to 100% (white)

CMYK model - (Cyan, Magenta, Yellow, and BlacK) is based on the light-absorbing properties of ink, as provided in printer cartridges, and mixed on dots overlaid on (typically white) paper.

As white light rays strikes translucent ink, and depending on the chemistry of it, certain visible wavelengths are absorbed while others are reflected back to our eyes. In theory, pure cyan, magenta, and yellow pigments should combine to absorb all light and the result would be black (darkness) reflected back to our eyes. For this reason these colors are called subtractive colors. Because printing inks are not perfect, and because we traditionally pring black-and-white documents that use large amounts of black text and grayscale (toned black) in our documents, a special supply tank (cartridge) is provided in most printers to complement printing. The letter K is then used for BLACK (instead of B to avoid confusion with the color BLUE, therefore: CYMK), and the setup called four-color process printing.