UFO like a vortex in the desert in 1975

On May 10, 1975, a person was near the ghost town of Cisco in the desert of Utah when he has seen an enormous and multicolored UFO looking like a vortex…

Witness statement:

This sighting took place in May of 1975 in the desert of Utah, at night, right off a highway while traveling towards Colorado. To this day it was been a scary and unexplained event in my life. 

I saw a full side view of a very HUGE bright lit multicolored (mostly variations of blues, as I remember) circular in shape tunnel looking (vortex) like thing, swirling over the flat desert floor.  It appeared to be several miles long (tube shape), extremely tall in height and just a couple miles off the highway I was traveling on.  I'd just like to know if anyone else has ever seen something similar, and if so, what could it be? Do you have any ideas? It's bugged me all of  this years and has made me fearful of dark deserts ever since.

Any help would greatly be appreciated.