The colour traditionally associated with Saint Patrick’s Day is green.
Green is linked to Ireland, the shamrock, and the modern visual identity of Saint Patrick’s Day. Celebrants commonly wear green clothing, attach shamrock badges or sprigs to their outfits, and decorate streets, buildings, and food in green on March 17.
The association developed over time rather than coming directly from a known command by Saint Patrick. The shamrock became an Irish symbol, while green was adopted as a powerful emblem of Irish identity and nationalism, especially during the political movements of the 18th century. The colour also appears in the green, white, and orange Irish tricolour.
Saint Patrick was historically associated with “Saint Patrick’s blue” in some contexts, and blue appears in older artistic and heraldic references. Green nevertheless became the dominant popular colour of the holiday. Orange is sometimes seen in Ireland because it represents another tradition within the island’s history, but it is not the conventional Saint Patrick’s Day colour.