On NCIS is Leroy Jethro Gibbs wearing a toupee?

In "NCIS," Leroy Jethro Gibbs, played by Mark Harmon, is not wearing a toupee. His hair has been a topic of discussion among fans, but it appears to be his natural hair, albeit styled in a way that may look different under various lighting conditions. Any rumors about a toupee likely stem from the changes in his hairstyle over the years.