The guy who did these exact pics (in the op) discusses how he did it and other stuff in this gdc video.
he is discussing how he used colour pallette cycling to animate the pics in question at about 6 minutes and that it's actually almost impossible to do with modern tools. it is really worth watching the whole vid if you are into pixel art
gdc video about the original pics posted.
8 bitish pixel art.
Link to original work now available through browser.
late seeing this..this is great..thanks for posting!