I understand how to connect a decoder, having done it on a number of diesel locomotives.   What I do not understand is the wiring of the female plug connecting the tender to the locomotive.  The locomotive is a Bachman 2-8-0 Bachman steam locomotive.  I am trying to understand the how to connect the wired the tender side of the connection.  What wires connect to the light plug and how the wires connect to the four proung plug.

I want to install a sound decoder into a steam engine tender.  I need to understand how to connect to the wires to the two plugs from the tender to the engine.  Can someone tell me what color wires are connected to each plug?  Thank you.