Rev 4:2-3
"At once I was in the Spirit, and behold, a throne stood in heaven, with one seated on the throne. And he who sat there had the appearance of jasper and carnelian, and around the throne was a rainbow that had the appearance of an emerald."
The vision of the throne: God is not described directly — only by comparisons to precious stones and light. The rainbow (covenant, Gen 9) surrounds the Judge’s throne — judgment is always framed by the mercy of the covenant.
Rev 4:8-11
"And the four living creatures, each of them with six wings, are full of eyes all around and within, and day and night they never cease to say, ‘Holy, holy, holy, is the Lord God Almighty, who was and is and is to come!’"
The Trisagion (hagios hagios hagios) — the oldest hymn of heavenly worship (cf. Isa 6:3). The worship is continuous, without rest. The 24 elders cast their crowns — acknowledging that all authority is delegated, all glory belongs to God.