What is the purpose of purple rope belt that Sasuke wears? All Orochimaru's people are wearing a purple color rope belt. What is the purpose of it? Why Sasuke is wearing it even after killing Orochimaru? Does it offer any power?
The purple rope is like an Obi, a garment worn with the traditional Japanese kimono. Besides that, and holding his clothes together, the only real purpose it serves is to hold his sword. You don't want to be always carrying a sword in one hand, especially during fights. Sasuke started carrying a sword after the timeskip, so that might explain why he changed his attire to include that purple rope.

Orochimaru used to carry the Kusanagi sword, and the other characters might be doing it to show their loyalty to Orochimaru.