This is a day with three sets of Commemorations. [a "set" of commems would be the collect, secret and post communion prayers. -- in other words 3 of each type of prayer would be said.]
If the Mass of St. Peter is said, the collects go in order: St. Peter, 1st Sunday of Advent, then St. Barbara. If the Mass for St. Barbara was said, then the order would be reversed.
"White - double - St. Peter Chrysologus, Bishop, Confessor, Doctor of the Church -
St. Peter, Archbishop of Ravenna in Italy, who died about the year 450, won the title of Chrysologus, "Golden worded, " not only for his eloquence, but because his words were good, true, and of priceless worth. God's choice of St Peter as a bishop, which was made known in a vision to Pope Sixtus III, is alluded to in the prayer of the Mass. - SM"
"Red - St. Barbara, Virgin, Martyr
St. Barbara, also commemorated today, was a virgin martyr, who suffered for Christ probably in Egypt, during the reign of Galerius, about the year 306. The details of her holy life are unknown; but she has been held in veneration throughout the Church from the date of her martyrdom. - SM"
The Epistle for St. Peter's Mass is the reading from 2nd Tim: 4, 1-8 -- the one about being careful for good teachers, and not false ones.
The Gospel is Matthew 5: 13019 -- JEsus admonishing his disciples that they are the salt of the earth, and holding them more accountable, because they will be teachers.
Ut's worth noting that before the '62 missal, for the doctors of the Church the Credo (Creed) used to be said. Pity they dropped that.
One thing that the EF form does not currently have is a Mass to be said for "Virgin and Doctors." There weren't any females declared Doctors of the Church by the year 1962, but there are some now, and they deserve their snaps! BTW, the Church honors NO males as "Virgins."
Telling, isn't it? You'd think in 2000 years, but noooooo.
I've always particularly liked the introit for the Common of Doctors:
"In the midst of the Church he opened his mouth: and the Lord filled him with the spirit of wisdom and understanding: He clothed him with a robe of glory. It is good to give praise to the Lord; and to sing to tThy Name; O Most High. Glory be to the Father, ...[etc]"