Manipulating GIF image frames w/ PIL - where'd my palette go?

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I'm unclear how PIL handles multi-frame GIF images. I have such a GIF image
in a file, bogus.gif. I can view the individual frames like so
(ImageSequence is from the PIL tutorial):
... frame.show()

All but the first image appears black-and-white. They apparently lose the
color palette associated with the overall image. The palette for the
original image and the individual frames is the same, the histograms suggest
they have more than two colors and both the image the frames have mode 'P'.
What have I missed?

Thx,

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