The VGS display on the top is just one of many a typical example - this one happens to show a DivX (MPEG-4) file with "GMC", a feature which gives rise to the purple colored frames less commonly seen than the others. This file was also created as a so-called "packed bitstream", giving rise to the vertical light blue bars on many of the frames. Like many MPEG-4 files, there is a lack of any apparent repeating pattern, usuually seen in MPEG-1 and MPEG-2.  In a case like this, the red keyframes are may have been put in by the encoder at "scene changes", so this type of display can often be used to detect the frame number corresponding to a scene change. On the other hand, the decoder may have been set to  "max 100 distance between keyframes", in which case they may not. Lower max distances between keyframes improve the random access capabilities of the file.