Hell, it could be anyone.
Black:
Roxas (black bodysuit)
Siefer (black beanie)
Pence (black headband)
Sora (black coat and pants)
Hades (black toga)
Xemnas, Xigbar, Xaldin, Vexen, Lexaeus, Zexion, Saix, Axel, Demyx, Luxord, Marluxia, Larxene, Roxas (black trench)
Jafar (black outside cape)
Timeless River characters (black and white)
Vivi (is black)
Pain (black outfit)
Yuna (Zanarkand symbol)
DiZ (black belt and scarf)
Ursula (black body)
Sephiroth (black outfit)
Tifa (black outfit)
Leon (black outfit)
Yuffie (black outfit)
Maleficient (black outfit)
Prince Eric (black boots)
King Mickey & Riku[Xehanort Heartless,Blindfolded] (black trench)
"Hanging Out"
Roxas (Hayner, Pence, Ollette)
Seifer (Fuu, Rai, Vivi)
Sora (Donald, Goofy)
Ursula (Flotsam, Jetsam)
Leon (Yuffie, Cid, Aerith, Yuffie)
Hades (Pain and Panic)
Ariel (Sebastian, Flounder)
Simba (Timon, Pumba)