what was the tablib's boy wearing that got amirs attention?

Sohrab enters in a blue silk outfit, bells strapped around his ankles and mascara lining his eyes. The guards make Sohrab dance until the Taliban official orders them to leave. While the official rubs Sohrab’s stomach, he asks Amir whatever happened to old Babalu, a name Assef used to call Ali, and Amir realizes that the Taliban official is actually Assef.