Just like most other chicks the first indicator will be the color of the comb, sometimes you can go by size too. My grey EE's comb it larger and started to get pink just after 5 weeks so that's why I believe it to be a cockerel. They other has no color for now and almost no comb visible so it could still be a pullet. Of course you can get ones that mature very slowly. The sire to these chicks, my Blue AM, had a very tiny comb and it didn't start to get pink until around 12 weeks.
After about 12 weeks the cockerels will start growing their longer, pointy hackle and saddle feathers. These are the feathers at the base of the neck and tail. On the pullets these feathers will be shorter and rounded.
After about 12 weeks the cockerels will start growing their longer, pointy hackle and saddle feathers. These are the feathers at the base of the neck and tail. On the pullets these feathers will be shorter and rounded.