vommy, this is not a gain or white balance issue. This is an issue with minidv compression / color space that some encoding does better than others. I notice this issue with older dvx100b footage that was captured as mov, same goes with the xh a1. Captured as avi had a much smaller effect.
yup this is down to compression... particularly apparent with red. Turn down the chroma if you are working with vivid colours. Don't worry too much about it - it won't be so apparent when it gets to TV.