My dogs were outside in our fenced in backyard at around 6:30 and I heard them barking. I went outside to bring them in and noticed that several other area dogs were barking as well. It was a very clear night and I looked up at the trees and noticed that there were many lights flashing around. After looking closer, the lights at first appeared to look like small planes. But then I noticed that they were flying really low, so I thought they were helicopters. Then one would shoot up really high, higher than a helicopter could go. Several of them would fly close together, then shoot apart. They were triangular in shape and had at least 3 different colored bright lights, red, white and either green or blue. They were also silent. They appeared to be coming from the SW direction to NE. There is a hill that they would disappear over and that area appeared to be illuminated, although we can't see down to that valley from our house. I had my mother come out right away, and she saw the same things. By the time my husband came outside, they had already started to disappear. It then seemed that there were either helicopters or several planes flying around, more than we'd normally see, but they weren't the same types of crafts as we had seen 15 minutes before. I did call the township (Radnor) to ask if there was anything going on near either the Androssen Farm or the Highschool, and they didn't have any events noted. I told him about what I thought I'd seen and said that I've lived in this house for 12 years and hadn't seen anything like it before. He asked that we call back if it continued. When I first saw them I was amazed, not worried, just sure that it was something unique. When my husband came out, he was trying to sign a bright spot-light we have on them, but that didn't illuminate them, it just made it harder to see them. I'm not sure how long they were out there before I came outside, but they flew around for about 10 minutes, then just disappeared over the hill and too far away for us to see.