As a vestige of this system, you can enter Supergroup Mode. The only effect of doing so now is to allow you to alter your costume colours and chest symbol to match those of your SG. To enter this mode, click on the Super button in your chat window. It will open your Supergroup window which will show a list of people in your SG. In the upper right corner is a button that says, "Enter SG Mode". After you enter SG mode, you will see your Supergroup icon in your experience ring.
To leave SG Mode, you can click on the Super button, then the button in the upper right, which will now read "Exit SG Mode."