Something like the males, yes.Nice! Here are Blue Plymouth Rock pictures I found. You think something like this?
The chickens in those pictures are a sex-linked cross, where the males are blue with white barring and the females are blue without white barring. That lets the hatchery sex them at hatch just by looking for the light dots on their heads (males.)
Your rooster and hens are not the right cross to produce sexlinks, so looking for head dots will not tell whether yours are males or females. But it does work for the ones being sold as "Blue Plymouth Rocks" by hatcheries. (The name the hatchery is using is not really correct-- they are not pure Plymouth Rocks, and the males have white barring instead of being plain blue.)