ColorCenter is a JavaScript application that lets you quickly and easily try out text and background color combinations, as well as background textures. Choose colors from a palette, or use ColorCenter's color calculator to specify colors in hexadecimal, decimal or percentage form. Built-in links to popular background and graphics libraries let you easily experiment with a wide variety of images.
This useful site has great ideas about color and designing Web sites.
This is a useful chart of the hexadecimal code for colors on the web. It comes up quickly and displays the hexadecimal numbers in the colors they represent.
This site is the Webmasters color gallery, it allows you to select any color you wish to view and then gives you all the colors in which it was made. It is really a good web-site for a developers page.