Color changing, silent, slow moving oval above Portland's West Hills.I woke up because my cat was meowing at the window. I told her to be quiet, but she just kept on meowing, so I opened my eyes. I looked out of my window to see what the cat was meowing at thinking it must be a box elder bug on the glass or something, but instead I saw a big green oval of light.I live in a high rise building and can see Council Crest and the eastern side of West Hills from my apartment. I can make out the houses and features of this part of West Hills well. I could see a big green oval of light in the sky. It seemed to be moving slower than a plane or helicopter, and seemed to be silent. I put on my glasses so I could see it better out of curiosity and when I realized it wasn’t a plane or helicopter, I ran out of bed over to the window to get a better look. I saw the oval move towards West Hills. Then it slowly went over the hill and then I couldn’t see it anymore. The whole time it was floating around, it was gradually changing color from green to orange-red and back to green, with the color change seemingly starting towards the bottom right of the oval, and then sweeping over the rest of the oval until the thing had mostly turned orange-red.I don't know if the oval was solid or just light, but it seemed to have very clearly defined edges. It was not like spot lights at all, which kind of have fuzzy, soft edges.I know the oval was not a plane because planes are not oval shaped and they move faster. I see planes all the time from my windows, sometimes even antique ones, but this was not plane shaped and did not make any sound like a plane. I know the green oval was not a helicopter because I see helicopters a lot, too, and they are noisy and I can clearly make out the helicopter shape. In fact, I saw a helicopter come from the SW part of Portland towards the center of Portland a few minutes after I saw the green oval. I know this wasn’t a car on the streets of West Hills because I could clearly see the oval in the middle of the sky at first. And I don’t think it was a drone because it looked to be wider than the houses it was above in West Hills when it was above them. I thought for a second that it might be the aerial tram, which I can see a little bit from my place, but the aerial tram doesn’t change colors, it is not green and it doesn’t float around in the middle of the sky, obviously. I don’t even think that tram runs at 12:30AM.I know the oval wasn’t making noise because I can clearly hear planes and helicopters from my apartment. Also, even though this green oval floated really close to the houses on West Hills, nobody’s lights went on like they heard a loud noise above their house. I had my window cracked and could hear the helicopter a few minutes later, so I know that the noise would have definitely have come through if there were any.I tried to take a picture of the oval but my hands were shaking and I kept dropping my phone because I was a little nervous about the green thing in the sky, not knowing what is was and all, and I was trying to make my cat stop meowing by petting her at the same time. By the time I got my phone camera ready, the thing had floated over the West Hills and out of my sight. I don’t know what the green oval thing was, so I am hoping maybe someone else does and can tell me. I could draw a picture of it if that would help identify it.