check out the "mod info: troops.txt"
the bottom line of a troop entry is its appearance. The first entry is its skin color, hair color, beard and hair style. The longer second entry is the settings of the slider bar for its face details. The next two entries are the same as the first two. So, between the two sets of information is the range of appearances (they dont all look exactly alike).
If you set the hair color range to include gray and the faces to include the 2 older/wrinkled faces you will get what you are looking for I think.
Details are in the thread at the beginning of this post.
