Two witnesses. We saw it hovering over the middle of Guelph. We followed it until it was nearly above us. It then rapidly took off, headed for Kitchener. We Followed part way. We saw it circle again and head back towards Guelph before heading due north. It pulsated white, blue, red, and green lights. It made no apparent noise. We witnessed other airplanes in the area. They were much higher than this object and did not pulsate; their lights flashed. We watched it for over 15 minutes before deciding to head home. The whole time we tracked it in our vehicles.