I think that Mike B's list is a good indication of what is what; but afloat there are a few more blue light services. Harbourmaster and fisheries patrol vessels spring to mind, as do Range Patrol boats but they are MOD, so kinda come under Mike's list.
Difficult to find anything definitive via Googling as to lights, but flashing yellow in the marine sense has a fair few meanings h/craft, subs, purse seining etc... I have also seen it on survey boats, but it kind of looks wrong, as if they were on the hard shoulder!
PLA may be muddying the waters with their requirements (pun intended)