They brought in a DI to whip cast into shape to look and act like US Marines. Forrest Tucker, Wayne and Agar would spend their nights drinking. 4AM wake up call and DI insistence for PT, proper weapons and tactics training and how to wear the uniform of Marine brought evening partying to an end in short order. There is actually two famous Marine officers who play themselves during the assault on Tarawa. Forgot their names.
Halls of Montezuma has color shots of 5N up close. For color shot on still it matched the S&S chip card. Very dark blue.