Speed senosor

I have a question that might seem mudane but here it goes. I am installing a navigation system in my KW you no the in dash type. I have to hook a wire to the speed sensor and for the life of me I can't get a clear answer from a kenworth tech(and we let these guys work on our trucks). I know its back on the transmisson but there are a few wires there. The tranny is a eaton fuller 13spd. Can some one help me in finding the right color wire and is there a closer wire other than running one from the tranny?

 

My radio was turned to toast by me and my brilliant Buddy. This is what i get for not allowing my