two green lights side by side moving in unison; apparently a single craft, gradually changing to red, then green, then vanished.Just a few moments ago on the 3rd floor of my townhouse in South Philly facing City Hall exactly 2 miles away, I was putting my 3 year old son to bed. He was over my shoulder looking out the window when he said, "what's that?" Lots of helicopters and airport traffic pass over our heads on the way to the airport, and there's a helipad or two in the city so I'm quite accustomed to the aircraft in the area. This one was intriguingly different. I stood by the window to watch for about 2 minutes, then put him to bed, then ran up to our 4th floor deck, grabbed the binoculars and watched it for about 2 more minutes before it suddenly disappeared before my eyes. "It" was two green lights side by side, kind of like headlights, but not blinking. Usually you expect with aircraft to see white lights and/or red lights, and blinking. The green was eye-catching. It hovered west behind the Comcast skyscraper, then went UP, then wafted back east toward City Hall. Then it turned red! Again no blinking, just both lights slowly changed to red. It hovered around a bit as though circling City Hall, then turned green again, then gradually red, then like I said, right in front of my eyes, vanished. I wondered if it was someone's toy drone or something but way too big and way too high for that, and way too bright in my opinion. Wondering if anyone else saw it.