The easiest way to determine how HTML Colors works is to try it out, as it's quite easy to use. So go ahead and launch it. When you launch HTML Colors, it opens a window containing a sample set of HTML colors. Five small color swatches appear on the right next to check-boxes indicating what HTML element each color corresponds to. Here's a quick elaboration of what each color description means.
Browsers determine which links are visited and which are unvisited using an internal history buffer.
The maximum count of links and the age of the links that appear in this buffer is browser-dependent, and usually depends upon user settings. To change a color, click on the small color swatch. The standard Mac OS color picker dialog will appear, and you may choose a new color for that item. You may also click on the sample text or the background color to bring up the color picker dialog for that item. You can choose which colors are being overridden using the check-boxes by each colorable item.