The horse is quite often a solar symbol, and in the Bible it is one of intelligence. According to its color, a horse may symbolize either destruction or victory (fiery-red and white, respectively). It is a maternal archetype, and it might also symbolize "impulsiveness, impetuosity of desire, the instinctive impulses that motivate man. This association of the horse with darker human drives, such as virility and sexuality, has been resented by numerous writers [(Nietzsche)]. In dreams, the black horse of death and destruction is synonmous with misery" (Julien, 207). Is connected in many ways with aspects of the earth, specifically the SUN, MOON, and WATER. In addition, it is related to air and wind, acting as the mediator between heaven and earth; Centaurs are wind gods. A highly sacred animal, considered a taboo to eat its meat.
It carries many characteristics of the person as well, such as fertility, fidelity, sensitivity, strength, selfishness, anger, stubborness, stupidity and vanity. In psychology it can be the unconscious, subhuman side. A figure highly associated with many aspects of war, especially in the Greek tradition. Colors: white - omen of death but also innocence and divinity; black - famine; red - war; grey - devil. Types of horses: two - intellect, especially when harnessed together; winged - poetic relations; grazing - peace.
http://umich.edu/~umfandsf/symbolismproject/symbolism.html/H/horse.html