You won't have long to wait. By six weeks, it will have a reddish comb and conspicuous wattles if it's a cockerel. The feathers will be vivid in color and contrast. Pullets are mostly drab and muted until they get adult feathering.
Also watch for posture. Cockerels hold themselves more upright than pullets. Pretend there's a plumb ling running from head to toe, it will line up, head to feet. Pullets legs, when standing, usually run from the center mass to feet. Also by six weeks, cockerels have thicker legs and bigger feet. No matter the breeds of the other pullets, they will have more slender legs and daintier feet.