The Four Horsemen of the Apocalypse are mentioned in the Bible in chapter six of the Book of Revelation, which predicts that they will ride during the Apocalypse. The four horsemen are traditionally named War, Famine, Pestilence, and Death.
White Horse:
Opinions differ on whether the first horseman, riding the white horse (which often represents war in Bible), represents Christ, the Antichrist, or the False Prophet, but the general consensus of conservative Biblical scholars is that he is the Antichrist. One argument against this horseman representing Christ is that each horseman is released due to the opening of a seal. As the seals represent God's curses upon the world, it is unlikely Christ's return could be viewed as a curse. Moreover, interpreting this seal judgment as Christ's return is at variance with the unambiguous description of his return in Revelation 19:11-16. An argument that it might be Christ, states that Horsemen represent events which happen in specific time, as the seals represent things that should be opened in specific time.
Liberal Christian scholarship does not interpret this figure as either Christ or Antichrist. M. Eugene Boring's commentary on Revelation suggests that the image is drawn from the current events of the first century which the Christians in the Roman Empire would have recognized. In AD 62, the Parthians had beaten a Roman army in the Tigris valley and people throughout the empire viewed them with the same unrealistic dread as westerners in modern times had for the yellow peril. The Parthians were the only mounted archers of the 1st century, and white horses were their mount of choice. The passage can thus be interpreted as "conquest from without" without assigning any specific identity to the rider.
Red Horse:
The rider of the second horse is generally held to represent War. The red color of his horse represents blood spilt on the battlefield. He carries a sword, which represents battle and fighting.
Black Horse:
The third horseman, riding the black horse, is popularly called Famine. The black color of the third horse could be a symbol of death and famine. Its rider was holding a scale, which means scarcity of food, higher prices, and famine, likely as a result of the wars from the second horseman. Food will be scarce, but luxuries such as wine and oil will still be readily available.
The "a measure of wheat for a penny" from the King James Version might not sound like a famine to modern ears, but in the NIV we read "a quart of wheat for a day's wages", which is a little clearer.
Pale Horse:
The fourth horseman (on the pale, or sickly horse, which may be the source of the notion of "pestilence" as a separate horseman) is explicitly named Death. The pale greenish color of the fourth horse means fear, sickness, decay, and death. The imagery of the horses and riders is similar to a passage in Zechariah.
http://en.wikipedia.org/wiki/Four_horsemen_of_the_Apocalypse
