Her hair was black as night, and the bright braid of it across her forehead seemed but another shade of the warm dark eye that listed its heavy and sleepy lids, and looked out of the accidentally opened door as if she were trying to remember how she had dropped out of " Araby the Blest” upon so cheerless a spot. She was very beautiful. I should have taken her for a child, from her diminutive size, but for a certain fulness in the limbs and a womanly ripeness in the bust and features. The same dusky lips which give the males of her race a look of ghastliness, either by contrast with a row of dazzlingly white teeth, or from their round and perfect chisselling, seemed in her almost a beauty.
To be someone or something of a really dark colour, be it skin, hair, eyes, etc., like the night. Sometimes, people may also describe an item as being black as night to show how dark that thing is. It is another way of describing it as shadowy or black. This is one of many phrases used to describe blackness or darkness with a simile. It is related to phrases like black as coal, black as pitch (tar), and pitch-black.