Generally, I use the color to specify the server usage (Production => red, Development => green, etc...)
But I could have Multiple connection to a production server.
Of course I can use other colors, but this means lot of color used!
Protocol could be added like a small mini icon displayed on the computer screen or on the side (I mean something like that: https://cdn0.iconfinder.com/data/icons/thin-hardware/57/thin-176_computer_desktop_screen_security_locked_password-512.png
For example :
- FTP : no change
- SFTP : shield icon
- AS3 : amazon icon
Since icons are already very small, not sure if the render could be good...