How do you display the widget? Is it a slate object or some other GUI widget?
You should be able to know who the owner of the avatar is (and hence the clan/friendship of that avatar) as well as who are the owner of the viewer camera or GUI (and hence the clan/friendship of the viewer.)
Then bind a function from avatar data to circle color to the color property of the circle.
You may need to create some slot in the GUI where the current player object puts itself in, so that the GUI knows which player is current viewing.