Definitely growth and reddening of the comb and wattles... Even though you have different breeds, the combs should go from yellow, to pink, to red pretty much in synch.
Too, the feathers on the neck, most visible on the break from neck to shoulders- will be pointy and thin on cockerels.
Later, the feathers on the saddle- the area on the back just before the tail- cockerels will grow long thin feathers that droop down, and pullets will have shorter, rounder, tighter feathering.
Chest bumping, and curiousness are often attributed to cockerels, and while that's true of many cockerels- depending on the breeds and age- pullets can do the same thing. My first batch of Marans was like a WWE match!
