parallelogram shape outline only, no matter (substance) visible between the inverting of itself changing from red to green

It was a time when many sightings were being announced(15 miles from Savannah river Nuclear Facility). I just happened to be lying on a lounge chair looking up at the stars waiting for a friend to return home and there it was, a parallelogram, way up, very far 10-15 miles easy, probably stratosphere . It inverted itself and each time changed to the other color. I remember it being red green red green. I have to iterate that it was way up there. It appeared to me as 2 dimensional, as I only saw the outline of it’s shape. I did not see any substance within the lines of the shape. It appeared to be completely transparent.  It lasted what I consider a long time (30 seconds) because the tree line was relatively wide as I was in the middle of an open backyard and I caught it just as it came into sight from the east going to the west