Why do Catholics do that? Catholic Traditions Explained

Why is purple the color of Advent?

The Catholic Church uses visual aids to highlight a season of the liturgical year or a mystery of the faith.  Purple – violet – represents a time of penance and preparation. During the weeks of Advent, the priest wears violet vestments and the altar is decorated with violet to remind us to prepare penitentially for Christ’s coming.
On the third Sunday of Advent (Gaudete Sunday), rose vestments and altar cloths are used to signal that Advent is almost over. This is a happy time when we anticipate the joy of Christ’s coming.
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