To fully understand what is happening, it is useful to recognize where various events occur. The apostle John is in the
Temple of God, because the book with the seals are in God's hand (Rev 5:1), and when
Jesus takes it, the 24 elders surrounding God's throne bowed down to Him (Rev 5:8).
When the second seal is broken, a seraph calls out a red horse whose rider is given a great sword. The red horse rider is
tasked with taking away the peace of the world so that men would slay each other.
This is not the first mention of colored horses and their riders.
In Zechariah's first vision (Zech 1:7-11), an angel on a red horse
patrolled the earth and noted that the earth was quiet and peaceful.
In Zechariah's eighth vision (Zech 6:1-8), he sees four chariots,
which are the four spirits of heaven. These four chariots / spirits of heaven are angels
(2 Ki 6:15-17; Ps 68:17;
Isa 66:15). Going forth between standing before God and patrolling the earth, the first
chariot, being pulled by red horses, appears to be patrolling the earth although little is said about the red horsed chariot.
Without much detail, it is difficult to understand Zechariah' prophecies; however, one can gain a better understanding of
the colored horses and their riders who emerge with the breaking of the first four seals, and they all work in concert.