(I’m guessing the Durarara episode is named this partly because Celty was talking about how there’s trouble brewing but no one really sees it yet, and partly because Vorona’s name means “crow” in Russian)
Also available in the longer form 闇夜に烏、雪に鷺 (やみよにからす、ゆきにさぎ) “a crow on a dark night, an egret in the snow”