(Rev 4:3 KJV) " And he that sat was to look upon like a jasper and a sardine stone: and there was a rainbow round about the throne, in sight like unto an emerald." This tells me that there was a rainbow colored rectangle around the throne. Noah saw a rainbow as a sign of God's covenant to not destroy the earth with water again. Bible scholar's tell us that the rainbow is a sign of God's grace to mankind.
(Psa 100:5 KJV) "For the LORD is good; his mercy is everlasting; and his truth endureth to all generations."
We can look for God's grace and we will see it or we can expect his judgement and we will see that. He will be to us what we expect. The slothful servant in the Parable of the Talents said, "(Mat 25:24 KJV) Lord, I knew thee that thou art an hard man, reaping where thou hast not sown, and gathering where thou hast not strowed:"
(Mat 25:26 KJV) His lord answered and said unto him, Thou wicked and slothful servant, thou knewest that I reap where I sowed not, and gather where I have not strowed:
God will be to us what we expect of him. If we consider his commandments hard and unreasonable and rebel against Him, He will be hard and unreasonable with us. If we accept His grace and love and live so as to please Him, He will accept us with grace and love and forgiveness for our failures.
The "End of the Rainbow" will be filled with more treasure than the human mind can comprehend.