Big black object with coloured lights

I was walking back from a swimming pool in the summer together with my small sister and a friend. It was late and already completely dark. It was in a street with very few streetlights, a lot of trees and almost no houses, so there wasn't a lot of light pollution. At a certain moment we all looked up at the same time and saw a big black object obscuring the stars in the sky not very high above us. It is difficult to tell the height, but it was maybe 300 feet or so. It moved very slowly over us and was covered by lights of all colors, which strangely enough didn't illuminate the object. The object was too low and too slow to be able to be a plane or helicopter. We heard no sound.
Date in 1980 is approximate.  Report appears, in fact, to have been submitted from Germany.  PD