Heston is in water that is either brown or blue depending on the shot.
When Heston goes to blow the sluice, it is quite apparent that the water is the same height both sides of it. Blowing that sluice couldn't possibly cause a flood of any kind.
The picture of the plantation on the wall in Leinigen's mansion is a large aerial colour photograph. The story is set in the early 1900s. High definition colour photography had not been invented at the time.
During the first meeting/"confrontation" between Joanna and Christopher there comes a point in the conversation when he asks her if she is 'laughing at him.' As she turns from the dresser to face him at the very upper left corner for approx. 35 frames the moving shadow of what may well be a boom mic can easily be seen as it follows the motion.