Compatible Fiat radios have a square (8-pin) Mini ISO CD changer socket at
the rear that is part of a longer socket made up of 3 individual sockets.
You may find a green, yellow and blue connector pushed into this one long
socket. The blue connector is where the CD changer connector fits. If this
blue connector is present, remove it to establish if it is a blank (empty)
connector that can be replaced with the CD changer connector.

Does anyone have the pin-outs?

TIA