From what I understand caffenol/folgernol negatives are stained brown-ish - my guess is your software saw brown (as opposed to greyscale) and assumed it was in colour and tried to compensate accordingly.
I have had similar issues occasionally with files scanned from green-tinted XP2 or Chinese B&W C-41 film - the software assumes it is in colour because it's green, and sometimes odd tints/compensation can result until a B&W/greyscale conversion happens.
the film stain is
brownish from the caffenol + bromide
2 or 3 frames on the entire 72 frame roll
got the colorized treatment ...
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my guess is that you have something of a minor split tone going on... there will ALWAYS be some degree of that, however minor. I used to do that with Polaroid 55 neg film... print it on color paper - and you'd get a lovely subtle split... auto leveling HEAVILY magnifies any subtlety of effect...
Q: you don't do any fancy stuff with curves when you invert the neg scan? I've found that I've had to do some really crazy non-linear curvage when trying to actually mimic a traditional print. Meaning - a straight inversion can't really capture the tonality of a print. I guess what's actually going on is mimicking the characteristic curve of the paper/dev combo...
I have a scan of an old glass plate that came out surprisingly well toned in color though it was a silver emulsion. The computer makes stuff up, it's as simple as that. Another reason not to trust 'em.