A send up of Conan the Barbarian by Robert E Howard in Fallout 3 and addition of a bit of Marvel's versions of the gods Hercules (Outfit) and Thor (Hair color and Unstoppables' membership) in Fallout 4.
In Fallout 3 and Fallout: New Vegas, Grognak was depicted with jet black hair. In Fallout 4, however, Grognak is depicted with blond hair. Similar to how Conan who was originally depicted as black haired in the books' descriptions and the Marvel comics based on the books. But for the first big screen adaption, the light brown-haired Arnold Schwarzenegger was selected as Conan's actor.