Blue and red version of the taijitu (symbol of the Great Pole) used in Chinese folk religion and metaphysics rather than in institutional Taoism (which prefers the black and white version). Blue represents yang and the Heaven (天 Tian) or the God informing the universe; while red represents yin or the Earth (地 Di), or the substance that is given form by God.
Own work
Aethelwolf Emsworth.