UFO Sighting in Casper, Wy. in summer of 1976

This happened back in 1976 when my grandfather had come to my parents house for dinner. It was during the summer because the sun was just setting and my parents myself and my grandfather were standing out by his pick-up. My mother looked down our street and at the top of a hill she pointed out a white ball shaped object just hanging in mid air not moving. We all stood and watched it for several minutes with the object not moving at all.
 I went with my grandfather to his house and as we started driving the ball started moving with us. We got to my grandfathers house and stood in the front yard and watched it change colors. It went from white to yellow to a light green and then back to white again. It then started moving off getting higher and higher.
 My mother called us an hour later and told us that after we had left she had gotten into her car with my dad's very powerful banoculars. She went up on a hill that over looks Casper and could see the object very well. Behind it she could make out the contrails of 2 military jets closing with it. She said that they got to with in a certain distance of the object before it accelerated up and out of sight so fast that it left the 2 jets far behind in a matter of minutes.
 The next day it was reported as a "weather balloon" in the newspaper. That is the fastest balloon I have ever seen.
Witness indicates that date of incident is approximate.  PD