Three distinct light colors: blue, red, green shone at the same spot will appear as white light. The three distinct persons of the Godhead: Father, Son and Holy Spirit are all fully God, not just a part of God like a 3 leaf clover (1/3 + 1/3 + 1/3 = 1). If one of the three light colors was turned off, it would no longer produce white light (for example, if the blue colored light was turned off, the color yellow would be seen, not white). This illustrates the truth of the Trinity, that all three persons are necessary to be the biblical God. For example, if Jesus is not God, then the Trinity would not be biblical 1 Jn 2:23,24. This also illustrates that the persons of the Godhead are distinct, yet not separate.
Blue light illustrates God the Father since blue can represent the heavens (sky).
“Our Father in heaven, hallowed be your name”. Mt 6:9
Red light illustrates God the Son since His shed blood provided the forgiveness of our sins.
the precious blood of Christ, a lamb without blemish or defect. 1 Pe 1:18,19
Green light illustrates God the Holy Spirit since green represents new life and growth.
the Spirit gives life. 2 Co 3:6