I've been attempting to locate any information or documentation that talks about the new radar and what it is supposed to tell me?
A shaded circle shows that radar is up, and the circle as before shows the coverage.
A red shaded circle means the radar is down
Holding your mouse over a base will give you the base info. As you zoom in and out somethings fade away and come back to help ease the clutter.
Below is the image/screen shot Hitech posted.

Also note, this seems to be a work in progress as Hitech has been fielding comments about it and is making changes.