I am not sure what you mean by Advent Saint. There are hundreds of saints who have a feast day during Advent, including St. Nicholas of Myra. However, if any saint would be named as the Advent Saint it would be St. John the Baptist as the Gospels during Advent speak of him preparing the way for the Lord.
The liturgical season of Advent marks the time of spiritual preparation by the faithful before Christmas. Advent begins on the Sunday closest to the Feast of St. Andrew the Apostle (Nov. 30). It spans four Sundays and four weeks of preparation, although the last week of Advent is usually truncated because of when Christmas falls. Advent is all about preparing for the birth of Christ, so Christmas is the logical conclusion of this season.
Catholics celebrate Advent as a way of preparing for the Feast of the Nativity of Our Lord and Savior Jesus Christ, or Christmas. Just as the Christmas season is an important part of the church year, the preparation period leading up to it is also. The preparation for Christmas that the Church has in mind for its members during Advent is not about buying and wrapping presents, putting up Christmas decorations, attending parties, or making…
The color for the first of week of Advent is purple. The color for the second week of Advent is purple. The color for the third week of Advent is pink. The color for the fourth week of Advent is purple. In some churches, purple is the only colour for Advent. Purple is the colour of royalty, signifying the coming of Christ the King.