This schematic at fig 21 may help:
http://www.autozone.com/az/cds/en_us...rInfoPages.htm Your lamp is at middle right.
On the van side:
Dark Green = Turn signal switch input
Black = Headlamp switch input
Grey = Chassis ground
Since it appears they don't match what you're seeing you can use a multimeter to determine which is which. The wire with constant continuity is the ground. Turn the ignition switch on and activate the turn signal. Whichever wire you get 12vdc on is the input from the turn signal switch. Turn it off and turn on the headlights. Whichever wire you get 12vdc on is the input from the headlamp switch.
On the new socket side:
You'll have to correlate the wire color to the socket contact and to the filaments. The common connection/contact to each filament will be the ground.
You could always compare the left side to the right paying close attention to which wire goes to which contact in the socket.