White , 3 sugars and extra milk please .
Edit .. sorry .. didnt realise i had to answer
That looks very much like a cd changer wiring plug... it's also exactly the same plug and wire colours for a Nav dvd drive so basically it can be either .
As you have a nav unit fitted and it works then it's obviously for a cd changer.
I would hazard a guess that the wiring is standard and the cd changer was never fitted .. if it has been removed then you would have x2 orange wires in the same place .. this is the MOST lead and again if removed there would be a link to join them ( resend the signal back around the loop ) .
non fitted cd changer plug which from the looks of it is corroded with one wire not connected ... get some insulation tape and wrap it up please .. just in case it's still live .