system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Scientifically, what is the difference between color film and black/white film? What changed and allowed film to be in color?

What gives? I understand the basics of how film cameras work, but for the life of me I don't understand what changed.
gpt
Black and white film consists of a single layer of material that changes opacity based on the amplitude of light that flows through it, regardless of the color of that light.  This produces a film 'negative'.  The negative is then processed so that it doesn't change color anymore and is then used to expose another layer of film to produce a standard image that can be projected.

In color film, the film may have three layers or three chemicals that change opacity to match hues of cyan, magenta, and yellow.  This produces a color negative.  When this negative is processed and exposed to another layer, you get the inverse of cyan (red), magenta (green), and yellow (blue), which can then be projected and matches the colors of the original photography subject.

Negatives are usually preserved as much as possible, since they represent the highest quality version of the original image.