Color issue with old negatives shot with DSLR

[Ofnuts]

Are these color negative or B&W? For B&W you should not use color balance (auto or else), but Colors>Desaturate>Desaturate to make them truly B&W. A more advanced technique is to use the Colors>Desaturate>Mono mixer to favour specific color channels (films of that erase where mostly sensitive to red (so blue skies appear black)). And keep in mind than once you have a channel mix setting that works you can save it and reuse it later.