Negrini Wiring: The wiring diagram is not in the owners manual by MMI. See Morini Wiring. What number is on the magneto flywheel determines one of two possible wiring schemes. See Morini Wiring and Dansi Magnetos.
NVT Wiring: NVT (Norton Villiers Triumph) mopeds and motorcycles are made in England. The Easy Rider ER1 and ER2 mopeds all use the Dansi 101286 magneto, according to the owners manual wiring. On that magneto/generator, the lighting coil is split into two concentric coils, one for brake light and horn (black wire), and one for head light, tail light, and speedo light (green wire). The other coil is ignition (red wire), with an internal ground, so it is isolated from the lights.
NVT Easy Rider ER1,ER2, Morini MO1 or MO2 engine
Dansi 101286 magneto, internal ignition ground