Chocobos with unique abilities

Chocobo breeding was a pretty important feature of the original game; it was essential for accessing some otherwise impossible-to-reach areas. Depending on the color of a bird’s feathers, they had different types of terrain-traversal abilities. Rebirth seems to be keeping at least part of that tradition alive so far.
In the new trailer, we saw a dark gray Chocobo vertically climbing up a wall and a green one taking flight.