William III (William of Orange), born in 1650, was the son of William, Prince of Orange, and Mary Stuart (daughter of Charles I). William, one of the most significant players on the continent, constantly strove to spread Protestantism and decrease the Catholic influence throughout Europe.
William participated in many wars against the powerful Roman Catholic King Louis XIV of France. Many Protestants heralded him as a champion of their Faith; it was partly due to such a reputation that he was able to take the Crown of England. William stormed England at the request of the English Parliament and as a result his father-in-law, King James II (a strong Catholic supporter) fled out of England.
If you’re Catholic, then wear your green. If you’re Protestant, then demonstrate your faith and wear orange!