Red symbolizes the shedding of blood, thus red vestments are used on Palm Sunday, Good Friday, any other commemoration of the Lord’s passion, the votive Mass of the Precious Blood, the days marking the martyrdom of the apostles, and the feasts of other martyrs who offered their lives for the faith.
Since red also signifies the burning fire of God’s love, red vestments are also worn on Pentecost when the Holy Spirit descended on the apostles and tongues of fire rested on their heads; for the celebration of the Sacrament of Confirmation; and the votive Masses of the Holy Spirit. (Source: www.catholiceducation.org)