Why did in universe have darkness
Because that space is nothingness there is "nothing" and since black is the absence of the wavelengths of the visible light spectrum, it makes sense for the universe space to "look" black
Colors exist only in the mind, they are our mind's perception of light. "Black" is how our mind interprets the absense of visible light. If our eyes could see X-rays we might see the "black" of space another color, since it's rife with other forms of radiation. And once a day or so we would see a bright "flash" of gamma radiation believed to be caused during certain cataclysmic solar events.