I stumbled onto a web site that was recommending a add-on for Firefox which added colors to the browser tabs. I decided to give it a try and I liked it, so I thought I would share this with you. The add-on is called ColorfulTabs 3.9.4 and the author describes his program as:
The most beautiful yet the simplest add-on that makes a strong colorful appeal. Colors every tab in a different color and makes them easy to distinguish while beautifying the overall appearance of the interface.
Give it a try and see what you think.