May 22 is Trinity Sunday (the First Sunday after Pentecost), a festival that highlights the doctrine of the Trinity — the teaching that God is Father, Son, and Holy Spirit.
Actually, this doctrine (official church teaching) is not explicitly taught in scripture; in fact, the word “Trinity” itself is not found in the Bible at all. Rather, this doctrine evolved in the early church, through a long period of reflection and debate on the relationship between God, Jesus, and the Holy Spirit. Church leaders held a variety of opinions on this question, much too complicated to explain in a couple of paragraphs!
In order to be faithful to the Old Testament, it was imperative that Christians continue to believe in the existence of only one God, not three separate Gods. And in order to be faithful to insights from the New Testament (particularly in the Gospel of John), it was necessary that Jesus and the Holy Spirit be regarded as part of God, not just as beings that God had created. Eventually, the doctrine of the Trinity emerged, the teaching that God is a “Trinity” consisting of three “persons”, the Father, the Son (Jesus), and the Holy Spirit. It was formulated gradually, in a series of church councils held in the cities of Nicaea (in the year 325), Constantinople (381), and Chalcedon (451). This understanding of God is unique to the Christian faith, and is still accepted by Christian churches of all denominations today.
The symbolic color for Trinity Sunday is white, signifying joy and celebration.