Where does alternator field wire originate and what color is it?

[LongRider]

1992 400E. I have a fried alternator field wire at the alternator. I have tried to determine what color it is and where it comes from (where it originates), but I have a physical disability that will not allow me to lay on my back and reach up well enough to be able to track this small wire. I plan on, after I replace the alternator (might as well, the one that is in there is what? 24 years old), simply running a new wire from the point of origin to the field terminal on the alternator. Does the field wire require a small amount of "impedence" such as a small light bulb between the 12v+ source of origin and the field terminal on the alternator to "excite" the field of the alternator?
So, I need to know the wire color and where it comes from.
Thanks, my friends.