Updated for 7.0
On the left-hand side of the screen in the navigation bar under Member, select Group(s). This will take you here:
Select the group you wish to edit by clicking their name under List. This will take you here:
In the box titled Details, select the Edit button to the right.
This will bring you to a window that allows you to change the group name, description, and identifying color. It will look like this:
To change the color associated with the group, select the paintbrush icon to the bottom right of the text boxes.
When you have finished updating the group details, select the Update button in the middle of the window.
To cancel making changes to the group, select the smaller Cancel button right below the Update button.