The MPAA Prohibits Blood in Trailers so it is Often Colored Black

Because of MPAA rules U.S. movie trailers cannot show blood, so blood is often colored black to gain approval. Trailers that do not obey this and other rules, such as; foul language and violent, sexual, or otherwise objectionable imagery may be issued a red band, which indicates approval for only “restricted” or “mature” audiences. These trailers may only be shown before R-rated, NC-17-rated, or unrated movies.

Kill Bill Vol. 1 Trailer

Actual movie

Shaun of the Dead U.S. trailer

Shaun of the Dead U.S. international trailer