It is the feed to the tail light and number plate light. The red/blue wire is the sidelight circuit as is the spare connector behind the dash.

Not sure about the connector type? Most (but not all) on the Z are made by Hitachi. You may as well just fit a Scotchlok, or better still strip some insulation back and solder a spur in to provide a feed for accessories. This is what I (and many others have done).

__________________