Autometer electric FP gauge install question
 

I am in the process of installing this gauge. My question is this. The line running from the sending unit to the box show only 4 wires being hooked into the box. When I spliced into my line from the electric sending unit there are 5 wires! WTF. There is a red, black, bare wire, white and a very pale green. What is this pale green wire? Thanks for the help. I just don't want to ruin a brand new gauge.
Thanks!