Why is the movie Following (1998) shot in black & white? What theme does it resemble in this movie?
As explained in the relevant Wikipedia page:
Following was written and planned to be as inexpensive to produce as possible
For the most part, Nolan filmed without professional film lighting equipment, largely employing available light. This was made easier by the decision to use 16 mm black and white film.
This was explained by Nolan in the linked interview:
Christopher Nolan: Following was a film that I made knowing I couldn't get any money for it, knowing that I was going to have to pay for it myself. I wasn't a wealthy person. Everyone involved in the film was, you know, working full-time and trying to get by in London, which is difficult and expensive. But we figured out that if you shot in 16mm black and white, which made the lighting much easier to set up, we could shoot 15 minutes of footage every week, and pay for that, and keep going one day a week as we earned money through our various jobs. So it took us three or four months, shooting one day a week, to finish the production. It's probably the cheapest feature ever made, for what that's worth.