Over on The Donald someone wrote that coloring Christmas trees red is an Eastern European tradition and that the color represents the blood of Christ.
The red on our flag also represents the blood of Christ.
That’s likely true.
In the Lutheran church I was raised in there were two trees every Christmas. One represented the Tree of the Knowledge of Good and Evil and the other represented the Tree of Life.
The Tree of Life was decorated in white, with 33 ornaments, one for each year of Jesus’ life.
The Tree of the Knowledge of Good and Evil was decorated with red ornaments to represent fruit/sin. [This is a holdover from the Paradise plays of advent season in Europe in which a fir tree was decorated with apples to symbolize the Tree of Knowledge involved in the fall of Man.]