Can I change the color of my Mac OS X Terminal window depending on which server I am ssh-ed to?
Use different bash scripts to launch each session and change the background color depending on the server.
https://stackoverflow.com/questions/4404242/programmatically-launch-terminal-app-with-a-specified-command-and-custom-colors
you can use a script to connect to your servers, which also changes the bg color of your terminal before it connects.
http://www.macosxhints.ch/index.php?page=2&hintid=1001