Yeah, mine mangles different colors to different degrees as well, so it is hard to fix. Though I try changing the color balances and curves separately afterwards to get a bit closer to the original.

I'd love to have a decent A3 scanner because that I can't scan larger formats without piecing the image together frustrates me almost as much as the color distortion. I don't really have the inclination to draw tiny, and would much prefer to work on at least A3 for most stuff to get decent detail, but somehow parts never fit together right when I scan in two halves.