What does the green of the Christmas tree represent?

Life. Thousands of years ago the Celtic tribes would bring in evergreen branches into their homes during the solstice. In a world covered with snow and everything dead the evergreen was seen as life and hope. When the Celtic tribes were converted to Christianity the priests kept the evergreen as part of the new holiday Chris Mass so they brought the evergreen into the church as part of the celebration. The Romans also used the evergreen in their temples.