In the script he is actually an overweight ginger (Irish?). No niggers in the script as far as I remember.>>291674
It is a fine blend of film noir and horror. They did alter the character of Karswell somewhat unnecessarily, and I am not sure if it was really necessary to show the demon as blatantly as they did.
Very recently I noticed that demon in the film might be based on the engraving by Jean Duvet (1485-1561) of Christ on a white horse: https://www.metmuseum.org/art/collection/search/386240
The 1979 TV adaptation with Iain Cuthbertson directed by Lawrence Gordon Clark is also very fine IMHO, and in keeping with the original story it keeps the setting in the present day. Of course it lacks the budget of the 1957 film, but I quite enjoyed the 1979 setting and what they did with that.