Why is the movie pi in black an white?

I just saw this movie and was wondering the same thing. With that said here are my ideas as to why. Keep in mind all can be easily argued against. First, I think it may be because of the saying "math is black and white". As you know the movie revolves around math so that may be an obvious choice. Next, may be that max has lost his ability to see colors due to the fact that he stared at the sun as a kid. However, I'm not sure if that CAN happen if you stare at the sun. Last and most simply, could be that aronofsky had a small budget for the film and figured it was cheaper and more interesting. Hope this helps.