The term "complexion" in NBI refers to the color of a persons skin, especially the face. When applying for an NBI clearance, one of the required information is the applicants complexion, which can be chosen from options such as black, brown, fair, and others. If "others" is chosen, there is no need to specify the skin color. It is important to note that the complexion information is used for identification purposes only and does not affect the clearance process.