The Inspector wrote:
A great deal will rest upon which film stock the Wyler documentary was shot on as different movie film recorded the same item differently from anothers supplier. If Warners say used mostly KODAK film stock then the prop department knew that any 'blood' in the upcoming picture had to be mixed to a color card so it didn't look like ketchup or brown paint, old, cheaply done color films used whatever they could wrangle from a prop department so the 'blood' from a vampire might look like thin steak sauce because the mixology was wrong for the filmstock used.
Warning: thread creep ahead...
As a kid in the 60s I recall reading an artice about the making of "12 O'Clock High" TV series in
Air Force magazine.
They said they used Chocolate syurp for blood when it was filmed in B&W.