Tony's intricate personality translates into his wardrobe, which deviates depending on his mood. When he's feeling down, we see Tony in a white tank, boxers, and a robe. Witnessing the boss in this stripped-down, vulnerable state helps to humanize Tony, and allows us to feel sympathy for the sociopath. But when Tony goes about his day-to-day, we see him sporting a more traditional mobster look, complete with a bowling shirt, gold pinky ring, black slacks, and cigar in hand. To convey his head-of-the-family status, Tony sticks to his played-down wardrobe, and is never spotted wearing the more showy looks of his mob underlings.
Image Source: Courtesy of HBO