All the Hindu gurus I have seen wear some clothes that are indian. Clothes like kurta, dhoti,and other Indian clothes.
I have never seen one wearing a coat pant.
So can a guru wear western clothing?
Edit
Note: the currently posted answer cites Vivekananda and argues that the dress of a guru or any other person shouldn't be the focus of spirituality, however, I'm looking for a scripture-based answer on the kind of attire a spiritual guru/master should be wearing