hovering, flashing object in night sky

Often at night I sit on my back porch.  I face due east towards Chicago (45 miles east).  My porch has a spectacular view of the night sky.  I sit and watch the planes come in and out of O'Hare Airport as well as the beautiful night sky.  More times than not, I can locate an object that appears to be a brilliant star.  However, it moves.  It also flashes green, red and what I guess is yellow.  It's not a plane, I know it's not a star, it's not a sattelite.  If you sit and watch it with just the naked eye, it appears to be hovering and flashing different colors.  It's usually out there.  With sophisticated recorders (better than my hand held), I know anyone would see what I'm seeing.  What is it??  I will try to tape it this week...