Object that changes colors follows our car.

My father and I were driving home at dusk.  My dad said for me to look at that star to our left above the hill. He said that it was not there last night.  He pulled the car over so the headlights were pointing directly at it. He then flashed the lights on and off at it.  He kept repeating this over and over. Then all of a sudden the light started to change colors.  It changed to red, then to blue, then back to white.  Then it moved directly over our car and stopped.  My dad said we need to get out of here. We got back inside the car and proceeded up the road toward home.  The light took off again and moved along the top of the hill till it was out of sight.  There was'nt any sound coming from it.  This happened 41 years ago, but we both remember it like it was yesterday.
Witness indicates that the date of the sighting is approximate.  PD