St. Patrick's Day is now synonymous with green, but historically the colour associated with the saint was blue. Known as 'St. Patrick's blue', it was used in early celebrations of the feast day, which was made official by the Catholic Church in the early 17th century thanks to Irish priest Luke Wadding.
In the 18th century, blue was still prominent. A 1785 report in the Dublin Evening Post described men dressed in 'true blue' marching in a St. Patrick's Day procession. Even during the 1916 Easter Rising, Constance Markievicz used blue as the background for the Irish Citizen Army's flag, calling it 'the old colour of Ireland'. Politician W.T. Cosgrave later echoed this, saying blue was in 'perfect, traditional, national accord with our history'.
The shift to green began with the United Irish rebellion of 1798. This group, led mainly by middle-class Protestants, adopted the 'wearing of the green' as a symbol of Irish nationalism and opposition to British rule. Although the rebellion failed, green became increasingly associated with Irish identity, especially as nationalism became linked with Catholicism over the 19th century.
Irish immigration to America also played a key role. After the Great Hunger of the 1840s, over a million Catholic Irish arrived in the U.S., facing discrimination. They used St. Patrick's Day parades to assert their heritage, wearing green to show nationalism and connection to earlier rebel groups. This tradition cemented green as the dominant colour of the holiday.
Today, green is everywhere on March 17, from clothes to beer and even rivers. But the original colour of St. Patrick's Day was blue, a fact that surprises many who associate the day solely with green.
