light rust found on each terminal screw on each breaker, along with at the bottom of the panel.
i could feel air infiltrating the panel where the service conductors enter it.
could moist air entering the panel cause copper conductors to discolor this way?
i need reassurance of the color of the conductors.
is it possible that the copper conductors are patina???
or is this tin coated copper?
check the color of the ground wires.
Raceways entering from a cold area to a warm area (and vice versa) are required to be sealed off. A little insulation stuffed in the nipple would have prevented this problem. Your picture is pretty bad. Probably no permanent damage, but certainly worthy of writing up.