Ooh shinies! So far, I'm hoping that froakie will have a bright green color, like how normal politoed is almost. I think chespin would look great with the chestnut on its head a dark green like the green on venipede, and with a darker version of normal furret's colors. And then fenniken would look awesome as a cream color with the red fluff on it's ears a dark golden color, like ninjask's color. The Y legendary should be dark purple and light pink, almost like normal toxicroak. And then the X legendary should have elgyem's colors basically.
Gah shinies! (I love them so) XD
I think the legendaries will probably have a shiny lock, unfortunately, so the shiny versions can be given out at a later date perhaps? I think the new shiny animation will be like in the anime, where a bunch of stars come out of the pokeball with the pokemon, or stars kind of fleck off the pokemon if its in the tall grass.
edit: from my babbling and shiny fangirling, I seem to have decided shiny pokemon will in fact be in pokemon X and Y XD