These forms, however, are very rare. Indeed some shapes I have only heard unique reports about. Sometimes lights appear to change in shape. Other slightly less common colours include red, blue, yellow, and sometimes green. Some change color, for example some lights seem to vary in colour according to distance.
Speeds often vary throughout a sighting.
They appear to be some type of plasma or nebulous substances. Some balls are translucent to the centre. The structure of some lights appears to be dynamic. Sometimes they are static and so have zero apparent maneuverability. A lot just travel in dead straight lines.