When the sixth seal was opened, the sun turned black and the whole moon became like what?

Answer: Blood

At the sixth seal came a great earthquake; the sun became black like sackcloth, and the whole moon turned blood red.

“And I watched as the Lamb opened the sixth seal, and there was a great earthquake, and the sun became black like sackcloth of goat hair, and the whole moon turned blood red,”— Revelation 6:12 (BSB)