The Christmas season in the Catholic Church lasts until the Baptism of the Lord, which often occurs around January 12. Throughout this season the priest and deacon will wear white vestments, a color that is frequently used during periods of great celebration.
Dom Prosper Guéranger highlights the symbolism of these vestments in his Liturgical Year, explaining the rich symbolism behind it.
A word upon the Symbolism of the colors used by the Church during this Season. White is her Christmas Vestment...she expresses by her White Robes the gladness to which the Angels invited the world, the beauty of our Divine Sun that has risen in Bethlehem, the spotless purity of the Virgin Mother, and the clean heartedness which they should have, who come to worship at the mystic Crib.
White is also often used to remind us of our heavenly homeland and the vision described in Revelation of all those who worship around the Lamb, wearing white robes.
Green after white
The Christmas season is also quickly followed by Ordinary Time, which sees a change from white to green vestments.
Even the color green has profound spiritual symbolism that connects it to the Christmas season, as Guéranger explains.
...the color of the Vestments is Green. It is, say the interpreters of the Liturgy, to teach us that in the Birth of Jesus, who is the flower of the fields, we first received the hope of salvation and that after the bleak winter...there opened the verdant spring time of grace.
Everything in the Church has its symbolism and calls us to turn our hearts to God.
