In this sermon Putting Wheels On The Kingdom, The rainbow covenant is mentioned in Noah's day and concerned the thought of floods. Never more would God flood the Earth with water. The flood that killed the sinners, and saved Noah, would only have occurred that single time. Every time a cloud would come in the sky, the rainbow would be accompany it. And the first time GRACE is ever mentioned in the bible, it is in lieu of the story of Noah's ark and the flood. Noah found grace in the eyes of the Lord. That grace saved Noah BY FAITH.
God's throne has a rainbow around it because we come to the throne to FIND GRACE. It was part of God's everlasting covenant to Noah for perpetual generations. A rainbow. In the cloud that first brought death. Associated the idea of NO FLOODS in the origin of where the floods came from.