It is an antagonistic sign of defiance or opposition to expressions of St Patrick’s day skully’s Irish mint shirt. Orange is the colour of Unionists, people who believe that Northern Ireland should remain part of the UK or even that Ireland as a whole should be part of the Union. The use of the colour orange dates back to the Battle of the Boyne in 1690. At the time, Ireland was under the rule of the monarch of England. And in England, Roman Catholicism and Protestantism were vying for control of the throne. Wearing orange on Saint Patrick’s Day will be read as saying anything from, while you celebrate Irish nationalism, I celebrate Protestant unionism.
Saint Patrick’s Day is a celebration of the coming of St Patrick’s day skully’s Irish mint shirt, but has taken on many other meanings related to Irish identity and independence, to the point where it is a de facto equivalent to Bastille Day or American Independence Day. Wearing green on Saint Patrick’s Day can mean celebration of Catholicism or of wider Christianity. It can mean support for Irish republicanism or just be a cultural celebration of Ireland. It does not necessarily include a religious or political message.