Vertically disposed and of equal size, the colours green, white and orange on the national flag of Ireland symbolise the truce (white) between the older Gaelic traditions (green) and the supporters of William of Orange (orange). Although the design, which was based on the French flag, was introduced by Thomas Francis Meagher as early as 1848, the tricolour was only acclaimed as the official national flag after the Easter Rising of 1916, when it was hoisted above the GPO in Dublin. Holding undisputed sway to date, it is typically flown daily at all military posts and from a number of significant state buildings. It is also used to acknowledge the importance of special events, such as St Patrick’s Day, Easter Sunday and Easter Monday (in commemoration of the Rising of 1916), and the National Day of Commemoration of the Anglo-Irish Truce (1921).

The Dublin City flag shows the official coat of arms of the city (three double-towered, blazing castles) on a green background and is not to be confused with the blue version often used at sporting events. The three castles, which were originally three watchtowers, were adapted to bear three battlements, and have been the official symbol of Dublin since the middle ages. Rather than suggesting that Dublin is on fire, the flames leaping from the castles represent the zeal of the citizens in the defence of their city.