Circles based on extensions from volume Z-Score. Large volume candles can often signal exhaustion or show market strength in reversals or breakouts. Circles can be offset back to the start of the day/profile or left at the time where they occur.
Colours denoting deviations from the mean are
+2 std dev - Green
+1 std dev - Blue
-1 std dev - Red
-2 std dev - Purple
Concept is primarily as a pseudo volume profile delta tool. Obviously it's a very basic heuristic so would recommend further reading and use of actually footprint data to base trading decisions on.