Darkness can be understood to represent emptiness

Darkness can be understood to represent emptiness, the complete overcoming of ignorance: the false perception of reality, the illusion of dualism, of anything existing separately. Emptiness, the womb of enlightenment, can be understood symbolically as darkness ... Emptiness is not nothing. Emptiness refers to the radical insight that there is no individually existing, independently arising, separate self. All that is, is in constant flux, rising and falling in relationship to and with something else. Emptiness is the black of starless midnight, imminence, that comes before the pre-dawn of enlightenment, the "clear light", a state of translucence or transparency that is beyond dark and light. This is a radiant black. This is wisdom.

~ from LONGING FOR DARKNESS by China Galland