Disk shaped silent craft with 7 lights passed directly overhead of 3 witnesses, appeared high and huge.

I am a degreed civil engineer, 26 years old at time.  First and only UFO experience for all of us.  I stepped out of the house for an after dinner walk.  It was a clear calm evening around dusk.  As I was waiting for my girlfriend and friend, I noticed a light in the far distance just above the treeline to the south, which would be the Gulf of Mexico.  It struck me as odd that there were no blinking lights like you see on planes.  So I kept an eye on it as we walked and mentioned it to my companions.  It came closer and closer.  By the time we had walked about a hundred yards it was passing directly overhead.  It was silent.  It was circular shaped with about 7 lights evenly spaced around the perimeter.  As it passed over, it was traveling west to east and the lights changed color from blue to green (or vice versa).  It was hard to tell how high up it was and how big it was because I have no frame of reference for such an object; however, I suspect that it wa! s very high and immense.
Witness indicates that the date of the sighting is approximate.  PD