Cockerels have larger and redder combs from a very early age. Pullets don't develop large red combs until they are ready to lay.
The tail feathers are long, arched and pointed on cockerels. I couldn't tell from your pics but look on the side of you bird right in front of the tail. If there are long skinny feathers hanging down in an arc that is another clue. They are called sickle feathers and only the boys get them.