Well, last time I was there, the HM had very helpfully coloured all of the visitors moorings and pontoon spaces light blue. This was about four years ago, it certainly helped us to distinguish between the private and the public areas. Perhaps a Dartmouth resident can confirm if this is still the case.
Was there on Monday, visitors moorings are indeed blue, and marked with an LOA. Call DARTNAV on ch11 for friendly and helpful advice. Some visitors pontoons too, midstream and a few walkashores. I lunched on a buoy at dittisham and spent the night on the ferry jetty where you can stop 1800 through 0845. £20 for 37ft inc harbour dues.