I can, there's no blue wire on this truck though (never was). The Ignition & Charging wiring came from a 1976 Dodge Truck, they didn't use the (later style/traditional) Blue/Green color scheme. It's actually Green/Red. Hmm. I just checked it.
I've got 12.9 volts (Battery voltage) to both the Green and the Red with the Key on. Both at the regulator and at the alternator. Which makes sense, since they complete a circuit and the regulator supplies a pulsed ground to regulate voltage.
The only modification I made to that wiring (other than a Ballast Resistor Delete to run an Accel 300+ Ignition System) was to run the Alternator Charge Wire direct to the Battery instead of through the Bulkhead (Since I have a Voltmeter).
I even removed/bypassed the Fusible Link on the Charge Wire, to see if it might have burnt out.