And he that sat was to look upon like a jasper and a carnelian stone: and there was a rainbow round about the throne, in appearance like unto an emerald.
All Commentaries on Revelation 4:3 Go To Revelation 4
Victorinus of Pettau
AD 303
Moreover, the rainbow round about the throne has the same colours. The rainbow is called a bow from what the Lord spoke to Noah and to his sons, that they should not fear any further deluge in the generation of God, but fire. For thus He says: I will place my bow in the clouds, that you may now no longer fear water, but fire.