Hello Tushar
It can be purchased by anyone, not only citizens. However, apart from the 1-month GA Card, the GA is a subscription and has a minimum contract period of 6 months; therefore, it makes sense for permanent residents.
https://www.sbb.ch/en/tickets-offers/travelcards/ga-travelcard/ga-1-month.html
You might want letting us know why you are interested in the GA card and for what purpose; by doing so, we could suggest the best ticket for your needs.
Kind regards,
Roland