The black & white was to keep an R rating, as cartoony blood in color is clearly more psychologically damaging than cartoony blood in black-and-white.
Also, and this is purely a personal preference, but I hate subtitles in the black letterbox bars. I prefer them to be at the bottom of the image itself, with a little bit of a drop shadow behind.
Out of curiosity, what font are you using for the subtitles?