The Day of Pentecost (June 9th this year) is one of the seven principal feasts of the church year, celebrated 50 days after Easter (“Pentecost” means “fiftieth day”). It’s sometimes called the "Birthday of the Church," because it marks the birth of the Christian church by the power of the Holy Spirit. As the day’s scripture reading from Acts describes, the disciples, filled with the Holy Spirit, began “speaking in tongues” after a sound of rushing wind swept in and tongues of fire rested on each of them. Vestments and church hangings are red for Pentecost and people are encouraged to wear red to symbolize the fire of the Holy Spirit.
Red vestments represent the fire of the Holy Spirit. Lay persons wear red on Pentecost as well.