A khata or Kathak is a white scarf often made of silk. It's a religious symbol, and a khata is often given at special ceremonies. You can also see it as a gift. The color of the Khata is always white.
You can find Khata's not only on people but also together with the praying flags on the passes in Tibet (all passes are called LA). Also statues of important figures like former rulers and Buddha's carry khata's.