I want to wire a 2003 Daihatsu Charade with a 12N socket so the rear lights 
are operated when towed by my Van.

I can identify the wire colour codes for both indicators, fog light, 
reversing light and stop light. So I could connect up the yellow, blue, 
green and red wires from the 12n socket.

 Unfortunately the wires to the Left and Right Tail Lights are same colour 
code and

there are two common earth wires.

So how do I connect the Brown and Black? Or can I connect just one?

Can I connect the White directly to earth on the car chassis or to any of 
the two earth wires?

Do I need to use any type of diode in the wiring?

Any advice would be gratefully received

Thank you

Grant