In case anyone wants to investigate this, I've found a TIFF that Pillow reads with the incorrect colours.

The linked image is black text on white writing. Pillow views it as green writing on a pink background.

To reproduce, just open the image and show it.

http://www.nightprogrammer.org/wp-uploads/2013/02/multipage_tiff_example.tif