My experience with FZ7, which may have a similar internal set up to FZ20 is that poor exposure can affect colour quite a lot. If you have same EV± function as FZ (not the EV bias, next setting 'up'), it will automatically take 3 exposures with what it regards as the correct one in the middle and ±1/3 or 2/3 or whatever you set the bracket to. If this does not cure, you can also manually set the colour balance towards red or blue. Personally I don't find that helpful; much better done under your control in post-processing as you did above. Sorry only just spotted this thread.