Nighttime scenes were filmed using a filter to darken scenes. BUT this technique leaves the sky light when in fact the night sky should be dark. Further detail both near and distance is vivid when in fact it should fade, disappear, into the shadows and darkness of the background.
The fixation of Gil on the color of Henry's britches makes no sense. Stereotypically the colors of the Union was supposed to be Navy jacket with sky blue trousers. Then Stereotypically for the Confederacy was supposed to be gray jacket with SKY BLUE trousers. The Confederacy copied the sky blue trousers because when they seceded and seized the federal stores throughout the South they obtained said sky blue trousers en masse. So, already officially this character's stereotypes are debunked. Further the state militias had their own colors as well. In fact some Northern militias (such as Indiana) had gray jackets and trousers while some Southern militias (such as Louisiana) had navy jackets and trousers, while others (on both sides) had red jackets and trousers. Finally, many of the poorer, again on either side, might have just sent their kin off to fight in butternut. So, Gil could check all he wanted to check. But he might find sky blue, navy, gray, red, or butternut. But any of those colors would NOT have distinguished on which side its wearer fought during the war. AND having lived in that time, having fought in the war, Gil would have known that fact.