Artists Washington Irving and Thomas Nast are credited with being the reasons why Santa wears red clothes. Santa Claus was first given a red waistcoat back in 1809 by Washington Irving and given a full red-and-white suit by Thomas Nast later that century.
Today's Santa is derived from the Dutch Sinter Klaas. He has always been happy and generous, and the Santa that is popular today came about during the 19th century. Before this time, Santa was seen wearing clothes of almost every color, from purple to yellow. As time went on, the red clothes appealed to almost everyone. Today, Santa wears red, white and black.