White cigar shaped craft with blue light and black square.

Around 5pm on a clear, sunny day, I spotted a slow moving craft about 500 feet above me.  I originally thought it was a small airplane and disregarded it further, but when I noticed the craft stopped and hovered I paid closer attention and realized that it was no plane.  Planes don’t hover.  And it was not shaped like a helicopter, it was cigar shaped. Indeed I could not see any wings or rotary blades on it, just a white cigar shaped craft with a lone slow, blinking light at the rear of the craft.
The light was very interesting.  It wasn’t the normal cobalt blue you might see on a plane.  It was more of an aqua color, which would then become a lighter aqua after it blinked and then blink back to the darker aqua.  And it would blink more slowly than a typical craft light.
Even more bizarre was after about every 10 blinks, a large square black object seemed to replace the light for about 3 seconds only to be replaced back by the blue blinking light.  This black door would take up about one third of the craft and then completely disappear whenever the blue light came back on.  I thought maybe a cargo door was opening and closing, that’s my best guess, but the switch happened too quickly.  In fact there was something that defied the laws of physics about that black square.  It was so densely black that it felt like a black hole had opened up, not just a cargo door.  Also, the white body of the craft seemed to have a white mist around it – its outline seemed blurred by the mist – which was odd because there were absolutely no clouds in the sky.  And there was no vapor trail tailing behind the craft.  By contrast the lines of the black square were extremely crisp, no mist, no blur.
I pointed the object out to some passing neighbors and they too thought it was an odd craft.  We all agreed it couldn’t be a blimp and but instead seemed like a UFO.  After about 3 minutes the craft stopped hovering and proceeded eastbound at the same slow pace.  I looked away for about 15 seconds and when I returned my gaze the craft was gone.  The whole sighting was no more than 5 minutes.
Witness elects to remain totally anonymous; provides no contact information.  PD