The reason for this is Aishwarya's concern to conserve water. Reports suggest that both the actress and the director have decided not to waste precious water for the holi scene in their forthcoming film ACTION REPLAY. This comes in the wake of the fact that the city is already facing a huge shortage of water and there's no point in making the matters worst.
It seems Ash in tandem with her director is making all efforts to act like a responsible citizen. Well, Ash has surely scripted a lesson which many will follow.