The first day of Advent marks the first day of the Liturgical Year in the Catholic Church. Like all Church seasons, it is denoted by a color. This one is marked by my favorite: purple! Purple signifies both the sovereignty of Christ (his Kingship - hey, it is a royal color!) and penitence. If you want to be very technical, the purple of Advent is deeper and darker than the purple of Lent (of course, we get a liturgical break on the 3rd Sunday of Advent, but that's for another post!).
The second week we Prepare.