All of the Honda twins (and most of the singles) made before 1978 have the same configuration, more or less.
Single phase systems are like those most often described to us in high school. One long copper wire wrapped around a bit of iron and excited by a rotating (or reciprocating magnet). Either end of the wire represents the output from the alternator and it alternated between positive and negative voltage on both ends.
The Honda system is very similar, except that one side of the output is two wires instead of one. In the 1970s models, the same side of the output are the yellow and the white wires, with the pink being the common. Sort of think of the wiring like a 'Y'. Two wires on one end, joined, then a single wire coming from the other side.
The reason for this split is because the regulators, back in the day, were not exceedingly good at actually regulating the voltage. The system was designed to sort of balance itself out based on the given electrical needs. The alternator's output could be varied by only drawing currently from a portion of the windings, by segmenting the output wires. Pink to yellow represents a partial output of the alternator and pink to white represents a partial output of the alternator. Pink and then yellow and white together, are the whole.
With the headlight off, the bike is running from the pink/yellow combo and when you switch the headlight on, the output of the white is included in the mix and you now have full charging.
Even with this balancing system, the regulator could often struggle with the additional wattage. That's why these bikes came with such large batteries in comparison to their power needs. Much larger bikes, with electromagnetic alternators, like the CB750 would require a 14Ah battery, but the CB200 still used a 12Ah battery. A large battery, in addition to providing power for the starter motor and other such things, also acts like its own regulator. Large batteries can sink a lot of current in a system if there is more power being generated than being used. The CB160, for instance, didn't even use a regulator and relied solely on the battery for this purpose.