Well, that's a good question. The colors of red and green have a long history in Christmas traditions and culture. Red has been associated with the blood of Jesus, and green has been linked to the evergreen trees that were used to decorate the inside of churches during the Christmas season. The combination of red and green has also been popularized by the Coca-Cola company, who used those colors in their advertisements and branding. So, it's really just a combination of religious symbolism, cultural traditions, and corporate marketing that has led to the colors of red and green being associated with Christmas.