Special Chocobos
At one time, there were two now extinct types of Chocobo roaming the planet: The Mountain-Chocobo and the River-Chocobo. The Mountain-Chocobo was a green tinted bird with the ability to cross mountains. The River-Chocobo was a blue bird that could cross any shallow body of water. Remember that there are some parts of this planet that just can't be reached by conventional means. On the other hand, the right kind of Chocobo can cross anything. These two would sure come in handy, but no one seems to know how these two were bred.
There's a guy named Chocobo Sage, who no one has seen in years. It was thought that he either moved to some faroff land or just plain disappeared. However, it's known that he lives on the northern continent deep within the mountains. You can ask him for some Reagen Greens, but you'll need an airship to reach his cabin. You can also ask him about breeding Mountain- or River-Chocobos. He may even be able to tell you about the Black Chocobo. Make sure you revisit him from time to time. When you do find him, let Choco Bill's daughter, Chole, know and she'll keep track of any information he may give you.
Note:
Chocobo Sage's pet Chocobo has the "Enemy Skill" Materia. Check out its stall when you get there.
If you need the real scoop right away, here's what you need to know:
To get a Mountain- (Green) or River- (Blue) Chocobo you need to mate a Great or a Good Chocobo using the Carob Nut. You can't buy the Carob Nut in a store; insteal you'll need to steal it from the ferocious Vlakorados that roam the woods near Bone Village. You can also increase your chaces of breeding a special CHocobo if the parents are both S Class racers.
The Mountain-and=River (Black) Chocobo is created when a Mountain- (Green) and River- (Blue) Chocobo mate using a Carob Nut. Again it's not absolute, but you can increase your chances of obtaining a Black Chocobo by training the mother and father hard.
Once you have a Black Chocobo, you can attempt to breed the ultimate Chocobo. These Gold Chocobos can go absolutely anywhere. They can even reach the mysterious island northeast of the Chocobo Ranch. Have the Black Chocobo mate with a Wonderful Chocobo and feed them a Zeio Nut. These nuts are the rarest of all the nuts. They can only be found on a small island northeast of Chocobo Ranch. Note, however, that there are creatures in the woods known as Goblins. You should be able to steal the Zeio Nut from them during a battle.