In Revelation Christ rides on the white horse. St George is nearly always depicted on a white horse. Castor and Pollux were said to ride on
white horses. A horse, as I have said before, means knowledge. Thus to ride on the white horse means to have all heavenly counsel to aid you in gaining the victory and in obtaining the reward. It is said that there will be one more incarnation of Vishnu, when he will carry the sword of justice and ride the white horse, like Christ in Revelation. We must remember that the horse was used by the Hindoos instead of the Ram. Now as Aries or the Ram is the constellation in which the sun starts his zodiacal journey each year, the ram or horse means the opener of new thought, the dawn of a new era. Hence to ride the white horse means to begin a new kingdom on earth of joy and happiness and purity.
-- The Symbolism of Colour