Abe was created blue so that on the gamescreen he would be easily identifiable. It's just like the lights that float or eminate around possessed characters. Inside the Oddworld universe, Abe is blue as prophecised, making him the Saviour of the Mudokons. However, there are other blue Mudokons at Monsaic Lines. One wonders why they didn't undergo the same initiation rites as Abe - if they did, they either died or cowarded out.
Most all Mudokons can use their chant, though slaves and scrubs may not know how to. Native Mudokons can shift mountains with their mystic chant, so it's not like there's no power behind it. It's not been made clear whether other Mudokons can possess characters, but Volsung voices a good observation. There must be other Mudokons who have the ability to possess.
Shrykull is a
godling, it is only described as half-god. Alf has spoken of it as if it can be a living creature. He can seem pretty obscure and distant in the game, but I think I recall that Shrykull favours Abe: for the temple trials and for rescuing Mudokons (in the game this is represented as Shrykull portals). Don't quote me on that bit, though.
No molecular instability; no different breeds or species.
