What does Revelation 4:3 mean?
John continues here to explain the vision he saw when transported, in some sense, to heaven through the Spirit of God. This verse tells us God appeared with the likeness of precious jewels. Each carries a certain symbolism that we are meant to understand.The jasper stone John saw refers to a clear jewel, perhaps resembling a diamond. It portrays God's absolute purity and perfection. The carnelian was ruby red. It portrays God as our Redeemer. Israel's high priest wore the jasper and carnelian and ten other gemstones on his chest (Exodus 28:17–21). Each of the twelve stones represented a tribe of Israel. Just as the high priest wore the tribes of Israel symbolically on his chest, so Jesus, our High Priest carries us Christians on His heart. Jasper and carnelian are also the first and last gems, respectively, on the high priest's garments. This description not only reinforces that God is the "first and the last (Revelation 1:8; 22:13)", it also identifies Jesus as God, as both perfection and our redeemer.
John also indicates that an emerald rainbow circled God's throne. An emerald is green and symbolizes life. The rainbow first appeared to Noah and his sons after the Flood as a token of God's promise to refrain from sending another flood to destroy the world (Genesis 9:8–17). The emerald rainbow around God's throne likely indicates that His promise of eternal life is guaranteed.