The Basics

The use of color on the World Wide Web has often been portrayed as a source of mystery and arcane science. In reality, Web color and how it can be used follows relatively simple principles that are easy to understand and apply

The first thing to understand is how color is produced on the screen of a computer monitor. A CRT monitor screen are made up of small dots of phosphor called “pixels.” There are three pixel colors, red, green, and blue. A standard computer monitor has three electron guns, one each for red, green, and blue. Each electron gun “shoots” electrons that illuminate pixels with the matching color. The diagram on the right demonstrates how a CRT monitor works.

An LCD monitor is also made up of pixels, but the pixels are activated when a voltage is applied to them. When they are switched on they display as either red, green, or blue. But when no voltage is applied and they are switched off they appear black.

The diagram on the right illustrates how LCD pixels are arranged on a monitor screen.

Varying the “amount” of red, green, and blue produces different colors. This is called the RGB system. The typical computer monitor today is capable of producing up to 32 million colors. The settings for a monitor are set using a Display Properties panel similar to the one on the right.

However, Web browsers use color pallets. These pallets consist of 256 specific colors. All colors displayed using a browser, such as Netscape, Internet Explorer, or Opera, are created using this pallet. Of the 256, only 216 are theoretically the same on both Macintosh and PCs. These 216 colors are called “browser safe” because they are supposed to be presented identically by browsers on both PC and Macintosh computers.

So while a computer monitor may be capable of presenting millions of different colors, browsers use only 216 when they display a Web page on that monitor. This can create some difficulties. To understand more it is necessary to see how colors are created on a monitor.