The post I am a part of up North uses blue helmets, but the post I am involved with in CA uses Black.
I am a cadet and mine is yellow like the rest of our dept.
our juniors wear yellow helmats with an orange front
If you are a junior, Explorer or rookie member in our county you wear a red helmet to make you standout from the rest.
All line officers Chief to Sgt wear white helmets. Firefighters depends on their helmet they wear could be black or yellow. EMS blue. If there is a orange helmet its someone wanting to find out what it is to be in the fire service and stays out of the way.
If I see a green helmet its someone from a CERT group.
Juniors in my area wear orange helmets.