White or blue vestments may be worn on this Feast Day. The color blue is permitted only on Feast Days dedicated to the Blessed Virgin as it was her favorite color.
Green would be worn on her feast day as it occurs during Ordinary Time.
The vestment color would be the seasonal color. Catherine's feast day is on April 29 and, normally, would be green (Ordinary Time) but would be white if the feast occurred during the Easter Season.
During Baptism the color of priest vestment is WHITE.
White vestments are worn
The Triduum, Holy Days of Obligation, and Feast Days of Martyrs
Off-white is NOT a liturgical color approved by the Catholic Church.
Roman Catholic AnswerTo the best of my knowledge, none of the doctors of the Church died as martyrs, so their feast days would be white. If they did die as martyrs, the priest would be wearing red.
Saint Patrick's Day falls during Lent so the vestment color would be violet.
A priest's vestment is generally white when it's Easter. On special occasions, however, a priest might wear gold in white's place.
Often, a banner matching priest vestment color is in front of altar, the color being associated with the church time, like purple as it is in Lent. It does not always match; if priest is doing funeral he will wear white but the altar may still be purple.
Either blue or red depending on what story you are talking about
White or blue and white since it is a feast of the Blessed Virgin.