UFO near Thermopolis WYI was returning home from a night at work around 11 or so pm. I parked behind my apt and was walking around the side of my building. I decided to stop and take a leak before I went inside (hey I'm in Wyoming!). I was doing my business and looking at the stars when I noticed to the NW a bright light. To me it looked like an airplane as it was low in the sky and moving toward my direction. It is hard to say how far away it was, but a guess would be around 5-10 miles. Thinking it was an airplane I thought it was odd that I didn't see any blinking nav lights on it, so I countinued to watch it. After around 3-5 seconds of watching it began to change trajectory and began going up at what must have been a high rate of speed. The light went through a color progression changing from the white light to white/orange,orange,orange/red, red then disappeared. The upward movement traveled of a span of around 2.5-3" of sky. I stayed outside for several minutes afterward waiting to see if more lights appeared or this one returned and saw nothing. The night itself was beautiful, no clouds and very dark with many stars that help to tract it trajectory upward. I am definately looking at the sky with more meaning these days!!!