Pillow (or the built-in libtiff) corrupts the palette when saving a mode P image as TIFF.
I have Pillow-2.7.0-py2.7.egg and Python 2.7.8 (default, Jun 30 2014, 16:03:49) [MSC v.1500 32 bit (Intel)] on win32.
Simply opening an existing mode P image and saving it as TIFF will exhibit the problem. The first band (R) of the palette seems OK and the G and B bands are garbage. When I use compression="raw" (and therefore libtiff is not used), the palette is OK.
May be related to #718 but I don't get any exception, the original image in memory is OK (only the saved one is corrupted) and the length doesn't change.