Any of the more than 16 million colors can be converted to its hexadecimal tag if the RGB values are known. Using the table below, the hexadecimal six character set can be determined. Both the RGB and hex codes are shown for each color. As stated above, the number of unique colors that can be displayed on screen is over 16 million. This can only be accomplished on a system capable of handling 24 bits or 8 bits each for the red, green and blue values.
More bits allow for more colors.
The number of colors which can be displayed and viewed is determined by the graphics card and driver settings for it. If your system does not support the True Color or 24 bit option, it is still preferable to use the highest color setting available. The 65k or 16 bit setting is optimal and should display all Web graphics correctly. Download the latest video drivers from the manufacturer's web site. Increase the color depth of your display, if possible.