[Danny]

I came up with a good theory [total rubbish of course] about why Abe was blue and the other workers were green:

I thought maybe colour had something to do with health IE the healthier a mudokon is, the bluer his skin. At the beginning of AO, Abe was Employee of the Year, so was probably treated better than other muds, which is why his sking was blue. When he is strung up, his skin is a more yellowy shade, you'll notice.

Also, the Native mudokons in the Monsaic Lines were also blue, because they have a higher standard of living than the Slaves.

Also, when mudokons become sick with Brew or Laughing Gas, they turn yellowish.

This is all rubbish, but makes perfect sense.