When you are working with a GIF image in a Graphics or Photo Editing program and want to save it, most editing programs will give you many options, including the image size and the kind of Color Palette you want to save with the image. The Color Palette used will determine the number of colors and which specific colors are imbedded with the saved image.

A color Palette is a simple collections of solid colors.

For GIF images, a Color Palette can have up to 256 predefined or Indexed Colors. Although, using a Palette with a fewer number of colors will give you a smaller file size when you save your image because fewer colors have to be defined for the Palette and for the file.

The Color Palette you save with an image will determine the number of colors and which specific colors are imbedded with the image. If you are able to define a Color Palette when you save your image and want to decrease the file size as much as possible but want to retain as good a color rendition as you can, then save it using an Optimized Color Palette or Adaptive Color Palette instead of a Standard or System Palette.

A Standard or System Color Palette by default, will use a predefined range of Red, Blue and Green colors. An Optimized or Adaptive Palette is a customized color palette and a little more complex.

Rather than storing the number for each color of each pixel in a file, it figures the recipe for the colors that exist in the image and then assigns a number to each of these colors. Then it stores only the assigned number of each pixel, rather than the more lengthy color number for each pixel. Thus, you get a truer color of the image because it preserves the color spectrum of the image and the file size is smaller than if you had used a Standard Palette.

With an Optimized or Adaptive Palette, the fewer colors you have in your original image, the more accurate will be the colors when they are displayed, that are saved in the file.

The table below lists some of the different types of Indexed Color Palettes that are used with GIF images:

Indexed Palettes	Number of Bits to Define a Color	Binary Power of Colors	Number of Possible Colors
Black & White (or Monochrome) 1-bit	1	2¹	2
Standard 2-bit CGA	2	2²	4
3-bit RGB	3	2³	8
Standard 4-bit EGA	4	2⁴	16
6-bit RGB	6	2⁶	64
8-bit Gray Scale (256 shades of gray)	8	2⁸	256
Standard 8-bit VGA System	8	2⁸	256
Adaptive (up to 8-bit)	8	2⁸	256
For Comparison: RGB Color Model (24-bit True Color)	24	2²⁴	16,777,216

Color Models Used to Define High Color Graphics

In the previous topic on Color, I talked about the Additive Color System which uses the Red, Green and Blue components of light to create colors and the Subtractive Color System which uses Cyan, Magenta, Yellow and Black pigments or inks to create colors. These are the two different ways to produce colors.

There are different color models that can be used for high color graphic images These two colors systems are used in graphics programs to define the colors used in graphical images that have more than 256 colors. They are called the RGB Color Model and the CMYK Color Model. There are other color models that are sometimes used to define high color images such as HSL, HSB, HSV, and LCH. The one you are most likely to see is the HSB model, which stands for Hue, Saturation and Brightness.

A Color Model defines a range of colors that are possible.

The HSB Color Model

The HSB color model defines three fundamental properties of color: Hue, Saturation, and Brightness.
It is predicated on the principle that every real color originates from a single pure color (Hue), which is then mixed with various amount of white or/and black color to give various shades of that pure color.
Hue is the name or pure value of the color such as red, green, yellow, etc. It is measured in degrees from 0 to 360. (0 is Red, 60 is Yellow, 120 is Green, 180 is Cyan, 240 is Blue and 300 is Magenta.)
Saturation is the purity of the color and is the amount of pure color mixed with white color. It varies from white to pure color. It is measured in percent from 0 to 100. The higher the percentage, the more pure will be the color.
Brightness determines the intensity of the color and is the amount of pure color mixed with black color. It varies from black to pure color. It is measured in percent from 0 to 100. The higher the percentage, the brighter the color.

The RGB Color Model

The RGB color model defines color using Red (R), Green (G) and Blue (B) light.
Each color is measured with a value ranging from 0 to 255 where 0 is no light and 255 is maximum intensity. This is how much information can be stored in 1 Byte of computer memory (256 pieces).
To define all three colors, you need 3 Bytes (or 24-bits) of information.
The RGB color model is an Additive Color Model.
Additive color uses transmitted light to display color.
Computer Monitors and the human eye use RGB to determine color.
The combination of amounts of individual red, green, and blue light defines the resulting RGB color.
When you add red light, blue light, and green light together and each component has a value of 255, then the resulting color is white. When the value of each component is 0, the resulting color is pure black.
With the RGB additive model, computers can display up to 16.7 million colors.

The CMYK Color Model

The CMYK model defines color using Cyan (C), Magenta (M), Yellow (Y) and Black (K) inks or pigments.
Each color contains an amount of ink that is measured with a percent from 0 to 100. A value of 100 means that the inks is applied at full saturation.
The CMYK color model is a Subtractive Color Model.
Subtractive color uses reflected light to display color.
Printed materials are produced using the CMYK color model.
The combination of the amounts of cyan, magenta, yellow, and black ink defines the resulting CMYK color.
When you combine cyan, magenta, yellow, and black ink together and each component has a value of 100, then the resulting color, in theory, should be black. When the value of each component is 0, the resulting color is pure white.
With the CMYK subtractive model, in theory, you should be able to product millions of colors, but due to the limitations of printing inks and the printing process you can only produce thousands of colors in print. Computers can display millions of CMYK colors, although they can't all be reproduced on a printer.

Common High Color Models	Number of Values for each Component	Number of Possible Colors
HSB Color	Hue = 361 Saturation = 101 Brightness = 101	3,682,561
RGB Color (24-bit True Color)	Red = 256 Green = 256 Blue = 256	16,777,216
CMYK Color	Cyan = 101 Magenta = 101 Yellow = 101 Black = 101	104,060,401

In the next section on Color Depth, I'll explain how "bits and bytes" are used to represent different Colors and by using more bits, you can represent more colors.