Just as certain types of clothes are worn during certain times of the year (i.e. summer and winter), the vestments worn by the priest and deacon at mass signifies meaning associated with the various seasons of the liturgical calendar. Have you ever been at Mass and wondered why a certain color vestment is being worn? Or why the altar is decorated in green, white, red, or purple? This is not a random choice but is a uniform system to create uniformity, structure, and movement through the liturgical calendar.
Liturgies celebrated during the different seasons of the liturgical year have distinctive music and specific readings, prayers, and rituals. All of these elements work together to reflect the spirit of the particular season. The colors of the vestments that the priest wears during the liturgy also help express the character of the mysteries being celebrated. These colors may also be used in linens and cloths which adorn the altar and ambo. Color communicates emotional and spiritual realities to the worshiping community. Liturgical color is more than simply decorative; rather it helps to express the changing seasonal moods which symbolize the shifting mood of the assembly gathered together to worship. Liturgical color helps to symbolize the deeper realities we celebrate and help us to worship in the spirit of the season.
From the General Instruction on the Roman Missal (#345) we learn:
The purpose of a variety in the color of the sacred vestments is to give effective expression even outwardly to the specific character of the mysteries of faith being celebrated and to a sense of Christian life’s passage through the course of the liturgical year.