Regarding the wearing of orange by Protestants in Ireland, Wikipedia has this to say:
William III (14 November 1650 – 8 March 1702) was a Prince of Orange by birth. From 1672 onwards, he governed as Stadtholder William III of Orange over Holland, Zeeland, Utrecht, Guelders, and Overijssel of the Dutch Republic. In addition, from 1689 onwards, he reigned as King William III over England and Ireland, and as King William II over Scotland. He is informally known in Northern Ireland and Scotland as “King Billy”. A member of the House of Orange-Nassau, William won the English, Scottish and Irish crowns following the Glorious Revolution, in which his uncle and father-in-law, James II, was deposed. In England, Scotland and Ireland, William ruled jointly with his wife, Mary II, until her death on 28 December 1694.
William and Mary were Protestants and ruthlessly put down the Catholics of Ireland.