Re: Light stool
While it's possible you just have some kind of immediate reaction to your flu, if light/gray/pale stools continue (not necessarily yellow), then it could indicate a liver problem. Gall bladder or high-motility problems are usually more indicated by colorful yellow or green stools (albeit liver can also be yellow).
I would see how it goes over a week or 2. If it goes away and doesn't seem to come back permanently, probably nothing more than body reaction to flu and no harm no foul. If not, you may want to call the doctor about it and ask.