2. Physics question. There's a rotating exhaust vent which is very shiny, highly reflective. At night it seems to have a prismatic effect as it takes yellow and white street light light and generates a rainbow of colors -- mainly we see glints of red and blue along with white. Is there an explanation for that effect?
If you are talking about the metal itself then this is caused by an oxide layer on the surface of the metal. As you heat metals they can oxidize, especially on the surface. Light refracts differently off of the two substances causing refraction in the same way that gasoline in water causes the same rainbow effect.
It is the wind that's spinning those exhaust vents. The effect is in effect all night long -- maybe it's happening in the daytime too, but we cannot see it then. Also, the running of heat or A/C is apparently very strictly controlled and restricted in Italy and now is not the time of year that you would get either. I have no clue what could possibly be getting vented up that exhaust, but nothing could possibly be running all night long, night after night.
I don't know if this is the effect you are seeing, but black dots spinning around on a disc can produce the illusion of color. I think it has to do with the "refresh rate" of the photosensitive chemicals in your eyes.