Round object with colored lights disappears instantly

My Dad, my sister, our dog and I went out to the mailbox, probably early evening.  I specifically remember the three of us looking up and seeing a round object with all different colored lights that went round and round on the bottom of it.  It seemed very high up in the sky.  I have no idea how long it was there.  I think only a minute or two, probably.  Anyway, it was there and then it just disappeared in an instant.  Not even a helicopter could have disappeared that fast.  I remember us all wondering what it was and how it could disappear so fast.
I asked my older sister about this a couple years ago to see if she remembered that happening.  She told me that she did remember, that it had happened, and that Dad had been pretty freaked out by it.  She told me that he had watched the news for a couple weeks after that wondering what it was.  There must not have been any reports though that she remembers.
Anyway, I can only guess the year to be between 1967-1970.  I must have only been 7 or 8 at the time.  I estimate this because my Dad died of Muscular Dystrophy in ’72, and at the time this happened, he was still healthy enough to be walking.  I was hoping to find other reports on your site, but didn’t.  Therefore, the exact year is unknown.  I’d be interested to see if anyone else saw and maybe what year, if they remember.
Witness indicates that the date of the incident is approximate.  PD