A word of caution
Very many years ago (in the mid 1950s as I recall), I remember reading a copy of an RAF safety magazine in which it said that some RAF pilots were painting their bone domes to personalise them. The article discouraged this practice because in a fire situation the paint could ignite and burn. These days, so far as I know, you never see a British military pilot with a painted bone dome.
The very fact that you are using a flying helmet suggests you are probably doing either aerobatics (or some other form of aerial daredevilry), where a fire situation is not beyond the bounds of possibility.
I suggest you take this into account when deciding whether to paint your bone-dome, or at least when deciding which paint to use.
Fly safely guys,
Broomstick.