The theory so long held of three primary and four secondary colors is purely exoteric, for since the earliest periods it has been known that there are seven, and not three, primary colors, the human eye being capable of estimating only three of them. Thus, although green can be made by combining blue and yellow, there is also a true or primary green which is not a compound. This can he proved by breaking up the spectrum with a prism. Helmholtz found that the so-called secondary colors of the spectrum could not be broken up into their supposed primary colors. Thus the orange of the spectrum, if passed through a second prism, does not break up into red and yellow but remains orange.
The ancients conceived the spirit of man to correspond with the color blue, the mind with yellow, and the body with red. Heaven is therefore blue, earth yellow, and hell —or the underworld— red. The fiery condition of the inferno merely symbolizes the nature of the sphere or plane of force of which it is composed. In the Greek Mysteries the irrational sphere was always considered as red, for it represented that condition in which the consciousness is enslaved by the lusts and passions of the lower nature. In India certain of the gods —usually attributes of Vishnu— are depicted with blue skin to signify their divine and supermundane constitution. According to esoteric philosophy, blue is the true and sacred color of the sun. The apparent orange-yellow shade of this orb is the result of its rays being immersed in the substances of the illusionary world.
In the original symbolism of the Christian Church, colors were of first importance and their use was regulated according to carefully prepared rules. Since the Middle Ages, however, the carelessness with which colors have been employed has resulted in the loss of their deeper emblematic meanings. In its primary aspect, white or silver signified life, purity, innocence, joy, and light; red, the suffering and death of Christ and His saints, and also divine love, blood, and warfare or suffering; blue, the heavenly sphere and the states of godliness and contemplation; yellow or gold, glory, fruitfulness, and goodness; green, fecundity, youthfulness, and prosperity; violet, humility, deep affection, and sorrow; black, death, destruction, and humiliation. In early church art the colors of robes and ornaments also revealed whether a saint had been martyred, as well as the character of the work that he had done to deserve canonization.