This problem was resolved with the discovery that certain dyes, called sensitizing dyes, when adsorbed onto the silver halide crystals made them respond to other colors as well.
First orthochromatic (sensitive to blue and green) and finally panchromatic (sensitive to all visible colors) films were developed. Panchromatic film renders all colors in shades of gray approximately matching their subjective brightness. By similar techniques, special-purpose films can be made sensitive to the infrared (IR) region of the spectrum.
In black-and-white photographic film, there is usually one layer of silver halide crystals. When the exposed silver halide grains are developed, the silver halide crystals are converted to metallic silver, which blocks light and appears as the black part of the film negative.
Layers of 35mm color film: 1. Film base; 2. Subbing layer; 3. Red light sensitive layer; 4. Green light sensitive layer; 5. Yellow filter;
6. Blue light sensitive layer; 7. UV Filter; 8. Protective layer; 9. (Visible light exposing film).