My boyfriend and I were walking home one night after taking a stroll through the nature preserve behind the middle school. It was a summer night, but there was no one else around at the time. As we crossed E. Lake St, we both saw what looked like some sort of aircraft. At first I just thought it was one of the many airplanes that fly continuously in and out of Airway Heights nearby. My boyfriend was the first to notice it was completely silent. We both watched it for a while. It seemed very close, yet made no sound whatsoever. In fact it seemed like the entire area was still and silent. It had many green, red, and blue lights flashing. It was hard to make out the full form, but it was definitely large with a domed "saucer"-ish shape. It flew across the sky in front of us, remaining silent the entire time. When it passed over the trees and the lights were no longer visible, natural sound seemed to resume. I have seen a craft like this before, but it was in upstate NY. We both witnessed that craft as well maybe 2 year prior to this.