I haven't seen what the rectifier regulator looks like Wangarra but you have explained the wiring, we know the wire coming out of the regulator is the battery positive.
Yes if the purple wire is the only wire out of the regulator it must be positive to the battery.
The 2 yellow stator wires are going to the regulator / rectifier.
The Black wire in the images is going into the regulator / rectifier.
