Darn Parking Lights!
The bulb has 2 filaments.
The black wire feeds one filament.
The green wire feeds the other filament.
There is a common ground between the two.
If the ground is not there odd things can happen.
The turn and tail and brake light and fladher switching happens in combination with the brake pedal switch, the turn signal switch and the flasher switch.
This is from 67 dart wiring diag so things might be a bit different on yours.
The pink wire you point to basically does this....
Black wire from the alternator to the main splice.
Main splice to the fuse block
Fuse block to the pink wires
1 of the pink wares powered the dome light cir.
The other pink goes to the e flasher the to the brake switch
From the brake switch a white wire takes power to the turn signal switch and to the flasher switch.
The bulb has 2 filaments.
The black wire feeds one filament.
The green wire feeds the other filament.
There is a common ground between the two.
If the ground is not there odd things can happen.
The turn and tail and brake light and fladher switching happens in combination with the brake pedal switch, the turn signal switch and the flasher switch.
This is from 67 dart wiring diag so things might be a bit different on yours.
The pink wire you point to basically does this....
Black wire from the alternator to the main splice.
Main splice to the fuse block
Fuse block to the pink wires
1 of the pink wares powered the dome light cir.
The other pink goes to the e flasher the to the brake switch
From the brake switch a white wire takes power to the turn signal switch and to the flasher switch.