The easiest, most foolproof option is “Happy Diwali.” Really, that’s it. You don’t need a PhD in Indian culture to pull this off. It works for friends, coworkers, and even that guy who delivers your pizza (yes, they celebrate too!).
But here’s the thing: Diwali is the festival of lights, not a spelling bee. So if you mumble it a little? No big deal. The intention is what shines—literally, like a thousand tiny diyas.