Why do the Irish wear green?

Blue not green was the color associated with St. Patrick long ago. Green, the color most widely associated with Ireland and St. Patrick's Day today, gained in popularity through the phrase "the wearing of the green" meaning to wear a shamrock on one's clothing. In Ireland, to do so was seen as a sign of Irish pride or loyalty to the Roman Catholic faith. St. Patrick used the shamrock, a three-leaved plant, to explain the Holy Trinity to the pre-Christian Irish. The wearing of shamrocks and shamrock-inspired designs became a feature of the saint's holiday. The change to Ireland's association with green rather than blue is believed to have begun around the 1750s.