Mostly these are the sensitizing dyes. It's how you turn an orthochromatic emulsion into a
panchromatic emulsion.
If you do a prewash, it will carry a bunch of sensitizing dye with it when you pour it out. And you haven't even started to develop the film yet. When I do this with TMY-2, I get purple. At the end of processing the film is usually slightly purple-pink.
The color is basically meaningless. If you don't like your film color when you're done, give the film a few minutes in sunlight. The UV will generally kill off the color for you. But it's not necessary. You can print right through it in the darkroom (has no effect on the print). Similarly, you can scan right through it.
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