Perfect triangle craft with green-steady/yellow-steady/red flashing lights flying LOW and SLOW on Labor Day.My son and I had just gone to bed. As we were getting ready to sleep, we heard a loud noise coming over the hill. We live in the desert on the edge of the military air space for Nellis Air Force out of Vegas, so we get a lot of jets flying over head. When they do fly over they are gone before you ever hear them; so unless there is more than one you never see the jet that you just heard. That night as we lay in bed we could hear a loud engine noise coming towards us from over the mountain to the south. I sat up to look out the east facing window above my bed as a perfect triangle craft came into view. It was slightly banked (bottom facing us) heading N/NW. It was small and if not for the direction it was going you couldn't tell which was the front. The ends each had a light, front/green, two back/yellow, top w/ antenna/flashing red. We could see the top just enough to see the light and antenna until it went out of sight. The craft could be heard for only briefly once it was out of view.The noise was not a regular sounding engine. It was more smooth and was like a loud humming. We could hear it for about 5 sec. before it was visible. It moved rather slowly. It was visible for about 10 seconds after it came over the south hill and before it passed over the north hill (approx. 300ft.).I am a 45 year old educated (13+years of schooling) stay at home mom, and my son is 11. We see all kinds of lights but rarely are they close enough to see what kind craft they are on. This triangle was only about 200ft above the ground (very low, barley above the mountains of our canyon). There was not enough light to see a color, but it was low and slow. I have seen pictures of other triangle crafts, but they are bigger than this, and usually have a light in the middle, this diid not and was small in comparison.I would love to speak to you about all I've seen and this event, but you'll have to leave a message as my phone does not work in the canyon I live in. I will promptly call you back next time I'm in town.