Since the Fokker E-types were operational during the period when camouflage of combat aircraft (and the very concept of "combat" aircraft itself!) was in its infancy, I don't think there is a "rule" to be followed. During the period it was more important for the nationality of all combatants' aircraft to be readily apparent, to avoid "friendly fire" incidents. I would follow WnW's instructions for the specific aircraft you'd like to model, as their research/documentation is extremely thorough.
Someone, please chime in with a better reply than mine!
Regards, Rob