When i was young and dumb I was told think of elektrickery much the same as water flowing through a pipe . Now I can rewire a bike all by myself.
Any way - yes i reckon red / white will feed a light , taillight + brake + black for earth as your new "fitting " may not create its own earth to the frame when bolted up. You can Undo the block connector . If you look from the end the wires go in- you will see the there is a small tab on one side in there that clicks in to hold the metal connector in place. get a very thin jewellers type screw driver - push it in from the wire end to flatten the tab slighty and gently pull the wire end out complete with the "lucar connector" . or buy some compatible new ones - or if you are patient - you could undo the crimp and re use. You can generally get complete new plug kits from auto stores. hope this helps