Charizard will have two Mega Evolutions in Pokemon X and Y.
In Pokemon Y, by holding Charizardite Y, he will transform into the already revealed Charizard Y. But in Pokemon X, by holding Charizardite X, he will transform into the black and blue Charizard X.
Here are the official descriptions:
When Charizard holds a Charizardite X, it can Mega Evolve into Mega Charizard X! This item can be obtained only in Pokemon X. Unlike Mega Charizard Y, Mega Charizard X changes types when it Mega Evolves. It changes from a Fire- and Flying-type Pokemon to a Fire- and Dragon-type Pokemon.
With this transformation, Mega Charizard X’s body turns black, and its flames burn blue with increased heat.
Charizard’s Attack increases significantly when it Mega Evolves into Mega Charizard X. Mega Charizard X’s Ability also changes to Tough Claws, which raises the power of moves that make direct contact. Mega Charizard X can use Dragon Tail, a physical move that can force the opposing Pokemon to switch out while also dealing damage. With its new Dragon type, high Attack stat, and the Tough Claws Ability, Mega Charizard X is all set to lash out with a fearsome Dragon Tail!
Mega Charizard Y is the result when Charizard Mega Evolves using Charizardite Y, which can be obtained in Pokemon Y. When Charizard becomes Mega Charizard Y, its pointed horns and long tail give the Pokemon a look of sleek sharpness. Mega Charizard Y is in a league of its own when it comes to flying prowess, able to reach incredible heights.
When Charizard Mega Evolves, its wings become larger than ever.
Mega Charizard Y’s Special Attack stat grows significantly, and its Ability changes to Drought, increasing the power of Fire-type attacks. Mega Charizard Y can use the Blast Burn move, a fiery attack made all the more powerful by the Pokemon’s Drought Ability.
Watch a trailer below. View some screenshots at the gallery.