Wearing green is one of the most important aspects of Irish culture and celebrating St. Patrick’s Day, but not everyone knows why people wear green when celebrating the holiday worldwide. According to TIME Magazine,

St. Patrick’s Day usually conjures images of partying, Catholicism, Irish nationalism and, perhaps most famously, the color green: green clothes, green shamrocks, green beer and green rivers. But the holiday used to be a solemn feast day when you’d be far more likely to see the color blue.

Many Americans eat corned beef, wear green clothing or drink green beer to celebrate St. Patrick’s Day, the celebration of all things Irish.