You can change the color sensitivity by the use of spectral sensitzing dyes. They are typically added just before coating the emulsion, but old workers used to bathe the film in the dye solution.

You can dye in the blue, green, red, short IR and long IR regions of the spectrum. You should not try to dye a predyed film. So, if you have a pan film, you probably cannot undo the pan sensitivity and make it ortho, nor could you easily add an IR dye and make an IR film, although adding is possible under some circumstances.