In the movie Kill Bill, why does the colour keep shifting from standard colour to black and white? Is it to keep the gross-levels down?
Kill Bill is basically a homage to dozens of films from the past, which were generally shown in black & white on television to cut down on the gore. The same happened to Kill Bill to be able to achieve an R rating and be released in theatres.
IMDB's trivia section confirms this:
No, I don't think it got anything to do with "gross level" - maybe the blood is not red, but body parts still fly around.
My own common sense tells me the goal of this technique is to put more focus on those scenes, draw the viewer attention.
This way those scenes are also much more "artistic" and give the movie whole new layer.. many times those things make the difference between "just another movie" and a cult movie.
Couldn't find any official explanation, so I stick with the above two reasons.