Western formals. Suit or Tuxedos for men, Dresses for Women. T-shirts, Shirts in case you want something casual.
Yellow, White or Orange Kurta with White Pajama for men. Yellow or Orange Sarees or Kurtis for women. Whatever you are wearing will have to be disposed post the event so plan accordingly :) Carry an extra pair given whatever you are wearing will get soaked.
Indian ethnics for men and women. You can also choose to wear western formals. Highly reccomend that men go the Bengali way and dress in a Dhoti- Kurta. You can check ready made dhotis and kurtas on Dheu or Paroma
Indian ethnics or Western formals. Again, keep in mind the heat before choosing to wear something heavy !