Apparently people found the “Making a Cable to Go Between a GPS device and the Kenwood TH-D7” useful, and have asked for information about making a data cable.
View of the front of the connector-side (not the best picture):
View of the top of the solder-side:
So a view from the solder-side shows the pins to be:
G = Ground
R = Red
B = Black (sometimes white)
A lot of this depends on the cable manufacturer. If for some reason it does not seem to be working, simply switch (R) and (B).