At first it seems wrong. Saint Paul is the saint of today’s feast, and yet white is the color of the day. He was a martyr, so, why are we not given red for this day? If we are humble enough to be taught by its wisdom, we see that the Church teaches profound things even in the smallest details of liturgy, such as the choice of colors. This is not the Feast of Saint Paul (for whom we do wear red), but a feast centered on the appearance of Christ to Saul as he was approaching Damascus: “I am Jesus whom thou persecutest” This day is a celebration of our Lord. Saint Paul said that he was a witness of Christ’s resurrection “as one born out of due time.” So, this Easter Feast of Christ’s post resurrection appearance is out of due time, in Epiphany.
Indeed, it is the last of the Easter appearances. These words of Saint Paul, from his First Epistle to the Corinthians, chapter 15, explain why:
“1: Moreover, brethren, I declare unto you the gospel which I preached unto you, which also ye have received, and wherein ye stand; 2: By which also ye are saved, if ye keep in memory what I preached unto you, unless ye have believed in vain. 3: For I delivered unto you first of all that which I also received, how that Christ died for our sins according to the scriptures; 4: And that he was buried, and that he rose again the third day according to the scriptures: 5: And that he was seen of Cephas, then of the twelve: 6: After that, he was seen of above five hundred brethren at once; of whom the greater part remain unto this present, but some are fallen asleep. 7: After that, he was seen of James; then of all the apostles. 8: And last of all he was seen of me also, as of one born out of due time. 9: For I am the least of the apostles, that am not meet to be called an apostle, because I persecuted the church of God.”
Indeed, that fourth fact that he preached was the appearance of the Risen Christ to eyewitnesses (1. Christ died for our sins, fulfilling the scriptures of the prophets, 2. He was buried 3. He rose the third day, fulfilling the scriptures of the prophets and 4. appeared to witnesses). White is the color of the day, because it is about the Risen Christ and His final Easter manifestation, the day that the final eyewitness to His resurrection saw Him.
The rest was the path to what red symbolizes, Saint Paul’s death as a witness.