The Barbarian's orb was more greenish-blue than a perfect blue color. In BlizzCon, when player's actually got to play the Barbarian, it was found that the Barbarian's mana was in fact, Stamina, the new energy type that leads us to believe that different classes may have different energy sources, but the Witch Doctor and the Wizard both have Mana as their energy source.
 
It may also be noted that the Diablo III Barbarian does not use Stamina for some of his more powerful skills, instead depending on another type of primal energy source called Fury as seen in the Skill descriptions.
 
Fury, it seems, is very similar to Rage. From BlizzCon's demo, it is clear that Stamina is the new Barbarian mana while Fury is a new expendable type of energy that increases as you kill monsters and rapidly decreases when the Barbarian is not killing anything.