Fresh Plus Visited is a very simple plugin for WordPress 2.5 that adds a user color scheme to the admin interface. The colors are exactly the same as the built-in Fresh color scheme, with the addition of a gray color for dashboard links that have been visited. Now you can use the link color to see which dashboard news items you have not yet read.
http://smithsrus.com/downloads/wordpress-admin-color-fresh-plus-visited/