During the liturgical year, priests will be seen wearing different colored vestments. The color is based upon the season, along with what the Mass is celebrating at that time. Red is one of those colors that they are seen worn. The red vestments are representative of the suffering and the Holy Spirit.
This color is worn during confirmations and Pentecosts. It can also be seen worn during different feasts, which include feasts of suffering and feasts of the Lord's Passion. Other colors that priests can be seen wearing include white, green, and violet. Like red, they all have different reasons why they are worn.
Red signifies the fire of love towards God, and the shedding of blood for the faith.
Red signifies the fire of love towards God, so is the liturgical colour for Whitsuntide, the feast of the Holy Ghost, and the feast days on which the suffering and the cross of Christ is called to mind; for the feast days of the Apostles and martyrs who shed their blood for the faith out of love for the Redeemer.