The Second Seal. . . A Red Horse
Revelation 6:3-4

"And when He had opened the second seal, I heard the Second Beast say, Come. 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."

        The color of the horse is a symbol of blood and the Sword is a symbol of War.