It wont be in the manual as US cars didnt have rear fogs. I would get hold of a test lamp or multimeter and go through what each one does by connecting wires up to your battery (with inline fuses in place

).
An educated guess is:
One red wire powers the switch LED
The other red wire takes power for the relay
The big blue wire goes to the relay
Black is the ground
And the fat red with the blue stripe?
