(WHTM) — The Christmas holiday isn't just about giving gifts to those we love — it's also about getting into the spirit, which many people do by decorating. But have you ever wondered: Why are red and green considered the primary colors of Christmas? According to Southern Living, Celtic people centuries ago admired red-and-green-colored holly plants for surviving the winter season. These ancient Celtic people believed that holly plants kept the Earth beautiful during the winter, so they would decorate their homes with it during the Winter Solstice celebrations to bring protection and good luck to their families. ‘Groovy!’: The story behind the strange trailer for 1947’s ‘Miracle on 34th Street’ But the Celts' use of holly isn't the only reason red and green colors are so prominent during the Christmas season today. There are also religious connections, specifically throughout Christianity. In the Christian bible, the color red is frequently used to symbolize the blood of Jesus Christ, whereas the color green is a symbol of the evergreen tree, which represents eternal life since it stays the same hue throughout the cold winter months. Although there's a long history of using red and green colors during the winter months and the Christmas holiday, it didn't take off here in the United States until the early 1900s. When you’ll see extra paychecks in 2025 In 1931, Coca-Cola hired an artist named Haddon Sundblom to create a Santa Claus advertisement, as reported by NPR. Sundblom's advertisement broke with tradition and depicted a fat and jolly man with red robes set in front of a green background (while holding a bottle of Coke of course). Prior to Coca-Cola's groundbreaking Santa Claus advertisement, Santa was usually portrayed as a thin and 'elf-like' individual. These new advertisements were so successful that Coca-Cola continued working with Sundblom for decades. After a while, this depiction of Santa Claus became the standard for "Old St. Nicholas" and solidified the use of red and green colors during this festive season in the United States.