Yin and Yang

Two girls twirl in the shadows, in their new dresses.
One in a pearly white dress with ebony black hair,
the other a licorice black dress and snow white hair.
Both have one white shoe, one black
with eyes to match.
Their eyes sparkle like the northern star.
Their voices silky smooth like melted candle wax
as they laugh and sing.
Beautifully white fanged teeth.
Not a care in the world,
as long as they have each other.

Now answer this...
Are they creatures of the night or just uniquely different?