>>/6578/
> I was actually trying to un-sepia it
you are referrring here about the noise and not about the color right? Because otherwise, I would be quite confused here.

I think that the image editors (GIMP, Krita, Photoscape...) have an option that diminish the noise (noise reduction). Depending on your editor, you could use a slight blurring as well.

I suppose that this was the intended objective for that edit.