If it relates to their conception by humans, it would be Death, Famine, War, Pestilence. Though technically, the first horseman (in Biblical order) was originally not Pestilence, but Conquest.
I watched as theLamb opened the first of theseven seals. Then I heard one of the four living creatures say in a voice like thunder, "Come!" I looked, and there before me was a white horse! Its rider held abow, and he was given a crown, and he rode out as a conqueror bent on conquest.
Revelation 6:1-2 NIV
The exact morality ofthe white rideris unknown. Some cast him as a civil war or the Antichrist. Others cast him as the successful spread of the gospel. Considering the Biblical use of white to represent righteousness, yeah.
When the Lamb opened the second seal, I heard the second living creature say, "Come!" Then another horse came out, a fiery red one. Its rider was given power to take peace from the earth and to make men slay each other. To him was given a large sword.
Revelation 6:3-4 NIV
The redrider is, of course, War. Red and a sword. Pretty anvilicious. Vasnetsov's portrayal of War has been one of my personal favorites, just because it gives me an idea where Frazetta got his idea for Conan. The other horsemen wear robes, but not War.
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. Then I heard what sounded like a voice among the four living creatures, saying, "A quart of wheat for a day's wages, and three quarts of barley for a day's wages, and do not damage the oil and the wine!"
Revelation 6:5-6 NIV
The third rider is, of course, Famine. The scales give this away dead-on. The choice of grain is actually botanically smart; grains are more prone to famine than olive trees and grapevines. Or it could be that the rich still live fine (hence the oil and wine) but the poor have a quart of wheat for a day's wages and three quarts of barley for a day's wages. Or the preservation of the faithful.
When the Lamb opened the fourth seal, I heard the voice of the fourth living creature say, "Come!" I looked and there before me was a pale horse! Its rider was named Death, and Hell 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.
Revelation 6:7-8 NIV
Death is the only rider who is explicitly given a name. Death actually has no weapon, though many depictions give him a scythe or a sword. The actual word is khloros, which can mean pale, pale-green, ashen, or pale-yellow. This suggests the sickly pallor of a corpse.