Those scribbles are what happens to overlaid polygons, rectangles, and octagons after they are put through a scan converter to Beta video tapes, and then from Beta video tapes through an MPEG encoder board into greatly reduced-resolution MPEG format. Red means that it is in search mode and cannot say where the face is. Yellow means it is very likely to be the target face. Green indicates a lock on the correct target.
Different shapes indicate what type of processing is taking place.
The squiggly polygons show the perimeter of a star-shaped polygon fit to the part of the image underneath it that corresponds to skin color. The octagon is also accompanied by feature trackers on the eyes, nostrils, and lips, but those graphics are hardest to see.