I've hair ...
I always wear something between nkfrench and helmet. It keeps the helmet cleaner and keeps my head comfortable.

Headsweats skullcap keeps head cooler, hair not as drippy and less sweat running down face. Wear it 55F and up.
Pearl Izumi transitions beanie is thin lycra that comes farther down over ears, 45F-55F.
I got some lycra tube (forgot the brand) at a sporting goods store, it is multi-purpose and I will use it to make a neck gaitor or pull one edge up over my head like a light balaclava. It can be layered with the PI beanie.
Finally, a fuzzy fleece balaclava for rides 45F and below.