code: private void updateGUI(SimpleImageSequence<T> sequence) {
  		BufferedImage orig = sequence.getGuiImage();
  		Graphics2D g2 = orig.createGraphics();
  
  		// draw tracks with semi-unique colors so you can track individual points with your eyes
  		for( PointTrack p : tracker.getActiveTracks(null) ) {
  			int red = (int)(2.5*(p.featureId%100));
  			int green = (int)((255.0/150.0)*(p.featureId%150));
  			int blue = (int)(p.featureId%255);
  			VisualizeFeatures.drawPoint(g2, (int)p.x, (int)p.y, new Color(red,green,blue));
  		}
  
  		// draw tracks which have just been spawned green
  		for( PointTrack p : tracker.getNewTracks(null) ) {
  			VisualizeFeatures.drawPoint(g2, (int)p.x, (int)p.y, Color.green);
  		}
  
  		// tell the GUI to update
  		gui.setImage(orig);
  		gui.repaint();
  	}
docs: Draw tracked features in blue, or red if they were just spawned.