Why do the stills don't match the finished product?

For instance this Batman Returns still: http://static.rogerebert.com/uploads/review/primary_image/reviews/batman-returns-1992/hero_still-of-michelle-pfeiffer-and-michael-keaton-in-batman-returns.jpg

That is the onset still but in the finished film, the image looks way darker and blue. This was before the garbage of digital so the effect was done on camera yet the still looks different? Can someone explain?