You will be doing some light hiking and even just walking around the cities will require a lot of uphill and downhill action, so make sure you bring comfortable shoes. As in many old cities, you might come across cobblestone pavements or the like, so avoid thin heels.
Mid-thigh length shorts are the shortest I'd recommend as you're not quite by the beach, although no one will deny you entry to any restaurants or bars (just remember to dress more conservatively when visiting churches and cathedrals).
I focused on a very pale, neutral palette with some dashes of orangey-coral. They should look great with the tan you'll get from walking around!
Have a great Monday!