Yeh, this one is confusing. I'm beginning to wonder if they coded the game to alter the colour values 'on the fly'. ie. Game gets graphics from memory, then while blitting it changes the values ever so slightly so they are plotted correctly, thus preventing us rippers from stealing straight from memory?
I even cooked up an app to cycle a 256 colour palette to see if other palettes exist, and it kinda works.. sometimes!