Let's discuss colors in a bit more detail. Your web browser software, Netscape, MS Explorer and others, use the same method to represent colors. They utilize the 256 colors that are predefined by your computer operating system. Sorry, not true. There are 216 colors that all these operating systems do share in common.
Color is perhaps one of the most important factors in philately.
You can save aggravation, and possibly complaints, if you use the colors from the 216-color palette. Using a very nice monitor and video card which supports millions of colors does little good when the average viewer has a monitor which only displays 256 colors. The browser will convert any color that its operating system cannot support by replacing it with one of the 216 common colors. You may as well use them anyway. Colors are represented in HTML by hexadecimal code instead of RGB values.