Four very bright white lights in a row alternating with a red and a green when the white lights went out.I was working and went to an open door facing south for a cool breeze when I saw the oddest thing ever. Object was on a north/south course headed south. It was traveling away from me. It held a steady speed, straight course and constant altitude. Sky was dark, mostly cloudy but Mars was due south in the sky. Object was slightly lower that Mars in height. The object had 4 extremely bright lights, square in shape and lined up in a row next to each other on the horizontal. They all came on at the same time and lasted for 1 second and went out and replaced, number 2 was bright red and number 4 was green instead of bright white. So the sequence was white-white-white-white (1 sec on), off-red-off-green (1 sec on), (repeat series. The lights were not strobes and very large in size. Approx. size of a vehicle tail light at 4 second distance. There was a plane in the sky at the same time and in the objects direction. I am not sure if it was a small plane behind the o! bject and headed north west or a jet much further south of it headed in same NW course but it would have been on course for Chicago O'Hare airport, flight path is in that part of the sky. There was no sound and the white lights reflected off the cloud deck. Brightness is best described using a building perimeter light just under the object. This light is a clear bulb, 450 watt halogen and the objects lights were just as bright but about 50% of the size. Halogen light was about 100 feet from my position.