what goes thru the firewall where, doesn't mean anything - track it further and you should find it comes from the ignition resistor, via the ignition switch
if it's been done right, the purple wire from the starter [S terminal on a solenoid] is the ignition resistor bypass, it goes to the coil via the ignition switch using the same wire that goes to the coil from the ignition resistor
wiring diagram that should work for you
Bill
