What does a Red Door Mean?

In China a red door means good luck and happiness, In Ireland the red is used to ward off ghosts and evil spirits. For Lutherns a red door symbolizes belief in God, while in Catholicism the red symbolizes the blood of Christ. In Colonial times a red door was a welcoming sign. Some say a red door means the mortgage is paid off while others think it just means the owners of the house like red doors.