White Horse - Conquest/pestilence. The rider carries a bow with no arrows, and wears a crown symbolizing a nonviolent rise to power. Holds the power of the Conquering, and to conquer also depicted as a hollow suit of armor from which bugs emerge.
Red Horse - The rider of the second horse is generally held to be gaining and represents War. The red color of his horse represents blood spilled on the battlefield. He carries a greatsword, which represents battle and fighting.
"Revelation 6:4 - "And there went out another horse that was red: and power was given to him that sat thereon to take peace from the earth, and that they should kill one another: and there was given unto him a great sword."