Unit 5: Introduction to Graphics
Lesson 5.2: Introduction to Color
RGB and CMYK Color
Color is an important aspect of any Web page. In general, a Web designer should use limited colors to establish a theme that can be used throughout the site. Establishing a color scheme helps give each page the same look and feel, regardless of content, and lets your audience know they are still within the same site.
RGB vs. CMYK Color 
The RGB color model is typically used when dealing with color viewed on a computer monitor. The CMYK color model, on the other hand, is used on print material when printing in full color.
| CMYK | RGB | |
|---|---|---|
| Colors | Cyan Magenta Yellow Black |
Red Green Blue |
| Color Model | Reflective -- light comes from a source, hits an object, and reflects from the object into the eye. | Non-reflective -- light comes straight from the light source to our eyes. |
| Values | Images are separated into various values of the four colors. | Each individual color (red, green, and blue) has a value, or intensity, from 0 to 255. The various combinations of the values produce different colors. |
Indexed Color
Indexed color is a limited palette of up to 256 colors. When using a limited palette, the computer approximates a non-included color by combining the colors within the palette; this is called dithering.
The indexed palette can have up to 256 colors, but does not require that many colors; the palette can have any number of colors up to 256. The fewer colors within the palette, the smaller the file size.
You now know that one way to optimize graphics for the Web is to reduce the number of colors saved with the image. Using an indexed palette with only the colors used in the image is one of the best ways to limit an image's file size.
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