Slingsby, funny how info can be twisted. The KAL aircraft had all its lights OFF (including nav lights, anti coll and logo) and the cabin crew are accustomed to closing all the window shades during cruise, so even the light from the cabin was blocked.
Meanwhile the USAF had a spy flight in the vicinity that was being tracked by Russian radar and they confused the two airplanes. If they had been able to visually identify the KAL airplane maybe they would not have pulled the trigger.