The liturgical color for Advent is violaceo [violet], commonly called purple by most people. There has been a trend in some parishes in the United States toward the wearing of a more bluish violet in Advent and a darker purplish violet in Lent. This is licit as long as the shade is violet. Of course, blue trim for Advent is also allowed. On the third Sunday of Advent, when we light the pink candle the Missale Romanum allows vestments of coloris rosacei [the color rose].
Father wore a new chasuble and stole this morning. It was of violet, but had a very interesting texture which gave it the look of two shades of violet. The stole had gold thread trim, and I seem to recall that it was a present from the parish on the anniversary of his ordination. Last year I believe he wore violet on the third Sunday of Advent, the rose color is optional and few modern priest seem willing to buy a set of vestments which they can only wear one day a year.
We did O Come, O Come Emmanuel as the opening hymn. The Gloria is omitted in Advent.
The author of the Gloria is unknown. It is of ancient origin, going back as far as the first century. It takes its verse from scripture:
Glory to God in the highest, and on Earth peace among men of good will.-- Luke 2:14.The Gloria was composed in the East, and probably originally written in Greek, not Latin. It was used in the Morning Office and not the Mass. It is still not used in the Greek Rite. It entered the Roman Rite first as a part of the Christmas Mass, probably in the fifth or sixth century.
The Gloria was not always excluded during Advent either. As late as the twelfth century it was still said during Masses in Advent. At this time the exact wording of the Gloria was not yet constrained and there were many versions, which were song at different Masses. When the Roman Missal was revised at Trent the expansion of the Gloria was prohibited.
Under present usage the Gloria is suppressed during Advent, because it is a penitential season, but the Alleluia is retained, because are still a resurrection people. We are penitent because we look forward to Christ's second coming, with hope and fervor.
But you, beloved, are not in darkness, for that day to surprise you like a thief; for you are all children of light and children of the day; we are not of the night or of darkness. So then let us not fall asleep as others do, but let us keep awake and be sober; for those who sleep sleep at night, and those who are drunk get drunk at night. But since we belong to the day, let us be sober, and put on the breastplate of faith and love, and for a helmet the hope of salvation. --Thessalonians 5.4