Twilight: UW (Righteousness and intelligence)
Rainbow Dash: RG (Timmy deck. Quick spells, some ramping, and then AWESOME big creatures.)
Pinkie Pie: Mono Red (She's practically a chaos god. What else would she be?)
Apple Jack: UG (Stalling the game with fogs and counterspells, waiting for just the right time until she can get her MASSIVE creatures out and wipe the board clean.)
Fluttershy: GW (Token deck, getting plenty of little critters out there to help her and then swinging with her massive army!)

Celestia: Mono White (amass her army, and exile any opponents' creatures. _{*to the moon*})
Luna: BW (Crusading against her offenders with vampires, knights, and spirits to slowly torment and dwindle away at them.)

Trixie: RB (Tru on that. Flashy and erratic, trying to win at any cost.)
Zecora: GB (All about using her graveyard to her advantage, scavenging what she can get to find exactly what she needs to beat you.)
Spike: Blue Fatty Aggro Deck because Spike is the worst character and doesn't know what he's doing.
Shining Armor: RW (Lots of soldiers, burn, and anything to just hammer away at his enemy.)

And that's all I can think of right now. :U