Grey. Most places are shut too ... We were there September and October and by the end of October it's getting pretty difficult ... On the island anyway. Having said that, we've been to Athens and the mainland in November and it's been gorgeous over 8 years ago
Visited the island of Astypalia in mid-October 2012 and we were the only tourist onboard the flight from Athens to Astypallia.
Enjoyed the week very much. You can get great discounts on hotels and car hire. Had a 4x4 jeep for 15euro per day.
But don't expect to see many tourists on the island.
The bigger islands Crete, Kos, Rhodos etc. they have charter flights from beginning of April till the end of October. almost 7 years ago