flag represents one of the four provinces of Ireland, Leinster, whose capital is Dublin. 
Description: The Ulster Banner is based upon the St. George's Cross (see above) and has similarities to the Province of Ulster Flag (see above). In 1953 the ‘Ulster Banner’ was adopted as the flag of Northern Ireland by the Stormont administration. The Flag of Ulster is a historic banner used to represent Ulster, one of the four provinces of Ireland. The Red Hand of Ulster is a symbol that is either derived from the O'Neill dynasty, then the most prominent Irish clan in Ulster, or the Dextra Dei of early Christian iconography. Title: Leinster Flag/ Naval Jack. Description: This flag represents one of the four provinces of Ireland, Leinster, whose capital is Dublin. The flag was previously used by the United Irishmen in 1798, Daniel O'Connel's Repeal of the Union campaign in the 1830s and 1840s, and the Irish Republican Brotherhood (IRB). Arms of De Burgh. The Flag of Ulster is a historic banner used to represent Ulster, one of the four provinces of Ireland. The Red Hand of Ulster is a symbol that is either derived from the O'Neill dynasty, then the most prominent Irish clan in Ulster, or the Dextra Dei of early Christian iconography. Leinster. The emblem and flag of Leinster is a silver stringed golden harp (the Brian Boru harp) on a green field, dates from the 17th century or earlier. The Leinster flag was indistinguishable from the Green Flag which was the unofficial national flag of Ireland from 1798 until the early years of this century. In heraldic devices, such as seals, each element has a specific meaning. Even colors have specific meanings. The colors red, white, and blue did not have meanings for The Stars and Stripes when it was adopted in 1777. However, the colors in the Great Seal did have specific meanings. Charles Thompson, Secretary of the Continental Congress, reporting to Congress on the Seal, stated:
http://cain.ulst.ac.uk/images/symbols/flags.htm https://en.wikipedia.org/wiki/Flag_of_Ulster http://cain.ulst.ac.uk/images/symbols/flags.htm https://en.wikipedia.org/wiki/Flag_of_Ulster http://clancorrigan.ca/historical-roots/symbols-of-the-four-provinces/ http://usflag.org/colors.html
what does the leinster flag mean