The green only goes one place---from one field terminal to the regulator. This wire is the one the regulator controls "to ground" to control field current
Blue comes off the "ignition run" buss, which is the only switched 12V in the engine bay. Comes out of the bulkhead from the ignition switch, and depending on the year/ model, feeds
ignition system
regulator IGN terminal (blue)
alternator field (blue)
electric choke if used
on some cars (six pack) the idle solenoid
on some cars distributor retard solenoid (May be B, E bodies only)
and maybe one other smog doo dad on some cars.
Here's the simplified diagram:
In the diagram, the top field terminal is the blue coming from 12v "ignition run"
The bottom field terminal is the green wire going back to the regulator