I observed this green light in the sky on both July 11th and July 12th, 2015. Unsure of distance or size of the craft yet I am inclined to believe that it was relatively close and relatively small due to the sounds I heard. I assume that if the craft were far away I would not have been able to hear it. The light was bright green, not a lighter shade of green, normal green but the light emitting from the craft was very bright. Could not make out a shape or anything really other than the light itself. It was like how headlights from a car keep you from being able to see the license plate. I heard the noise before I saw the light, it sounded like thousands of crickets making their chirping sound at the rate of a machine gun, and the sound was coming from above me and off into the treeline about 2 blocks away. I looked up when I heard the buzzing/humming/rapid-fire chirping accelerating and that is when I noticed the light getting closer to me. A few seconds after I noticed it it seemed to back away a little bit and heat toward the east, though not very far, it almost immediately changed direction and moved to my right (west). On the first night (July 11th) I was too afraid to watch it, this was at around 1:20 AM when I had to let my dog out to pee. The second night however I noticed the craft on my way home from walking the dog around the block at around 9:15. I caught the second event on video nd posted it to youtube, though the quality is terrible because I had the dog pulling my arm out of the socket the whole time. The second nit I witnessed the craft do much of the same maneuvers as the first night, though for about 2 full minutes. My fear had worn off. At one point the craft decent rapidly, as though crashing, and as it fell the light changed from green to white, to this pinkish purple color. I thought it was gone and then I heard the sound of what I assume was some sort of engine (the buzzing/humming/rapid fire chirping) accelerating again. It came back up above the treeline again, this time never getting quite as high as it did before. I saw it hover over the treeline, moving to the south west, then seemingly changing it's mind and going north. It moved faster the second night, fast than any man made aircraft I've ever seen. I live close to UK Airport in Philly too so the plane always take off and descend right over my head so I know the speed and color of planes coming in and going out, helicopters as well. This object displayed no familiar behavior of any aircraft I have ever seen. The noise was like nothing I've ever heard. I wish more people got to witness the event with me, I might not have been so afraid that I was going to be abducted.