[pygame] Sprite colours dont maintain same palette indicies

[John Anderson <corporalmustard@xxxxxxxxx>]

I'm having an issue with my attempts at implementing palette swapping,
it seems that if I change the colours in the main palette (the display
surface palette), all the sprites onscreen, rather than staying in
their respective indicies on the palette, shift to the closest colour
on the palette to their original colours.  I'm sure this is the
expected behaviour when trying to emulate 32/16 bit colour on an 8-bit
display, but I'm trying to get SNES/ NES style palette control, does
anybody know of a way of turning this behavior off?  Or at least a
workaround of sorts?