Such a shame to have to deal with such sensless acts of STUPIDITY. Suggest to your neighbor one way to remove spray paint they could use WD40 spray lubricant as a good cleaner. Try a small spot to see if it will harm the siding. It should work on aluminum,vinyl,and wood sidings. Some of these "CANNED NEAT ARTIST" show great potental art skills and they would be off channeling their skills to canvass in stead of on private property, train boxcars, bridges, ect.