The Oreo Dragon Skin is an exlusive skin only obtainable trough nesting by breeding two dragons with a Black Melanistic Kickstarter skin and a White Leucistic Kickstarter skin together. The chances of this skin mutation occuring from this breeding is currently unknown, however within the closed beta this skin mutation had a 40% chance of occuring during breeding. Oreo Skin can be bred and found in any of the playable dragon species the only exception being the hybrids like the Hybrid Dragon as it is infertile and cannot nest.
There is currently no information on how this skin will look like in-game, even though there is a placeholder Oreo skin avaibable for the Acid Spitter Drake that can be used in the beta version of the game.
Below are the dragons with the Oreo Dragon skins and how they look in the game:
As the oreo skin is a skin mutation it cannot be conbined any further. There are currently no skins that would be combinations of skin mutation combinations.