6:1 I watched as the Lamb opened the first of the seven seals. Then I heard one of the four living creatures say in a voice like thunder, “Come!”

6:2 I looked, and there before me was a white horse! Its rider held a bow, and he was given a crown, and he rode out as a conqueror bent on conquest.

6:3 When the Lamb opened the second seal, I heard the second living creature say, “Come!”

6:4 Then another horse came out, a fiery red one. Its rider was given power to take peace from the earth and to make people kill each other. To him was given a large sword.

6:5 When the Lamb opened the third seal, I heard the third living creature say, “Come!” I looked, and there before me was a black horse! Its rider was holding a pair of scales in his hand.

6:6 Then I heard what sounded like a voice among the four living creatures, saying, “Two pounds of wheat for a day’s wages, and six pounds of barley for a day’s wages, and do not damage the oil and the wine!”

6:7 When the Lamb opened the fourth seal, I heard the voice of the fourth living creature say, “Come!”

6:8 I looked, and there before me was a pale horse! Its rider was named Death, and Hades was following close behind him. They were given power over a fourth of the earth to kill by sword, famine and plague, and by the wild beasts of the earth.

6:9 When He [the Lamb] opened the fifth seal [cf. Rev. 5], I saw [John saw a different vision with opening of each seal] under the altar [in God’s throne room; perhaps an indication that those who had suffered a martyr’s death were now safe from all harm; perhaps an allusion to temple sacrifice in which animal blood poured out at base of altar (Lev. 4:7) thus signifying they laid down their lives in sacrifice] the souls [lives or persons] of those who had been slain [persecuted believers] because of [for this reason] the word of God and the testimony [Christians’ witness about their Christian faith] they had maintained [faithfulness in the face of persecution].

Note: Who were “those who had been slain”? It depends on your interpretive approach.
• Preterist: first-century martyrs
• Historicist: martyrs throughout history
• Futurist: martyrs during great tribulation prior to coming of Christ and millennium

6:10 They called out in a loud voice, “How long [only God knows the answer to this question], Sovereign Lord, holy [purity] and true [trustworthiness], until you judge the inhabitants of the earth and avenge [vindicate] our blood [and His name]?”

6:11 Then each of them [martyrs] was given a white [symbolizing purity and victory] robe, and they were told to wait [we must trust God to act in His own time and way to vindicate martyrs and His name] a little longer, until the number of their fellow servants and brothers who were to be killed as they had been was completed [others destined to join them in martyrdom for the cause of Christ].

Note: “The blood of the martyrs is the seed of the Church.”
[these verses are the answer to the question asked in 6:10]

6:12 I watched as he opened the sixth seal. There was a great earthquake. The sun turned black like sackcloth made of goat hair, the whole moon turned blood red,

6:13 and the stars in the sky fell to earth, as figs drop from a fig tree when shaken by a strong wind.

6:14 The heavens receded like a scroll being rolled up, and every mountain and island was removed from its place.

6:15 Then [natural catastrophes (judgment) after sixth seal opened (6:12); we do not know when God will pour out His wrath on a wicked world, only that He will] the kings of the earth, the princes, the generals, the rich, the mighty, and every slave and every free man [God’s wrath poured out on world’s wicked people; no one can escape divine judgment; notice mention of seven kinds of people indicating completeness of God’s judgment] hid [rather than repented] in caves and among the rocks of the mountains.

6:16 They called to the mountains and the rocks, “Fall on us and hide us from the face of Him who sits on the throne and from the wrath [indication that God hates all that is wicked and evil] of the Lamb [also the “Lion of the tribe of Judah” (5:5)]!

6:17 For the great day of their wrath has come, and who can stand [obvious answer is “no one” can stand; cf. Nah. 1:6]?”