Luke 3:16 (NIV)
16 John answered them all, “I baptize you with[a] water. But one who is more powerful than I will come, the straps of whose sandals I am not worthy to untie. He will baptize you with the Holy Spirit and fire.
Depicted here is the dove which represents the Holy Spirit and is the dominant theme, the water below - which represents your earthly baptism and cleansing of sin, and fire from above which is a purifying fire such as that used by a refiner or purifier of silver or other precious metal (see Malachi 3:1-4)
White t-shirt is the default, symbolizing purity.
However the design looks great on Asphalt, Black, Light Blue, and Creme