Colress plays an unknown but apparently crucial role in Team Plasma.
Colress illegally enters the Pokémon League tournament without eight badges under the disguise of a hood ("Hood Man"). He makes it into the top eight, and in the quarterfinal match, faces Marlon and wins. He continues in the tournament, realizing that battling the best trainers of the land will be invaluable to his research into the best methods for training Pokémon. He loses against Cheren.
During the battle between Cheren and Black, Colress discusses with Gray the philosophy of training Pokémon with a cold heart to realize their best potential. Colress has his doubts, since he has seen many different ways of training Pokémon that have been effective.
Colress, controlling Genesect with his machine, is found by Rakutsu, who attacks. After a battle, Rakutsu succeeds at capturing Genesect, and Colress leaves, warning Rakutsu that he, Colress, is the new leader of Team Plasma.
Colress is dedicated to his research into determining the best way to train Pokémon in order to realize their full potentials.