I was at home when my wife called on her way home from work. In the middle of our conversation, she remarked about an object in the sky and was really scared, wondering what it was. She described it as a light in the sky changing colors and that many people had pulled over on the street to observe. I asked her where she was exactly and she had just exited the 101 freeway at Reseda and turned northbound when she saw it. She told me she wanted to take pictures so we ended the call. About 15 minutes later, she arrived home and I said I wanted to see it for myself. She directed me to go down Reseda Blvd. (from our nearest cross street of Vanowen). Within 5 minutes I was on Reseda Blvd. and when I approached Victory Blvd., I could see the light off in the distance (about a mile south of me) near the 101 freeway. The light was maybe about 15 degrees above the horizon at that point. It appeared to hover left and right from about 50 feet to the east of Reseda Blvd. to about the centerline of the street. It would climb and descend randomly and was changing colors every few seconds. As I waited at the bus lane intersection red light by Oxnard/Reseda, The object seemed to dip lower on its descents than before, to the point where it disappeared from view before reappearing as it ascended again. It would consistently do this on the east side of its loops. It was difficult to tell if it was dipping behind the freeway or some trees to the north of the freeway. At this point, at its apex the object would ascend to maybe 30 degrees above the horizon from my position. Given the distance from Victory to Oxnard and the relative change in the objects position in the sky, I'm sure there is a way to calculate its actual altitude. As I approached Hatteras, the object disappeared for the last time and I went ahead past the freeway to see if I could reacquire sight of it, but couldn't find it again. I drove around for maybe another 10 minutes or so around the neighborhood and no trace of it.I returned home and my wife and I decided to head back down to the area we had last seen it to see if we could find it again. At this point, maybe an hour had passed since my initial call with her when she had spotted the object. It was basically our first chance to discuss what she had seen and she said it had gotten low enough for her to see it was a huge disc, but too thin for anyone to be onboard. We decided to drive south on Reseda to go up the hill south of Ventura Blvd for a better vantage point. Seeing nothing but the normal flight traffic to Burbank and Van Nuys, we headed back down. As we approached Ventura Blvd heading north on Reseda, we saw a massive object with a persistent green light at the center and alternating red lights about 40 feet to either side, which seemed like it was from a plane. This was unusual and caught our attention for three reasons. First, it was extremely low. It approached us from the north straight ahead and banked east over the 101 freeway. We turned east on Ventura Blvd to follow a parallel path as it wasn't traveling very fast. However, it did occasionally pass behind the buildings along Ventura, indicating a very low altitude. Secondly, it was silent. I didn't hear any jet or prop noise even though it couldn't have been more than 1500 feet away. We lost it near White Oak as it seemed to pick up speed and disappear to the east. The third strange thing about this craft was the color and pattern of its lights. If it were a regular airplane, which we see all the time due to our proximity to Burbank and Van Nuys airports, they should have had a more rapid blink to them. Instead, the alternating red lights were on for about a second before switching off. Also, a plane at that altitude would be in the process of landing, but no landing lights were on.