Mega Stones

Mega Stones are currently a prize for beating Red in the Winter event.

You will get one of the four Kanto starters mega stones as a prize.

Venusaurite

Blastoisinite                                                                                                                             ☀

Charizardite X

Charizardite Y

So far it hasn't been released for how to get other mega stone.

Put your ideas in the comments below