Her pale expression contrasted with her long, dark hair that hung down beyond her shoulders.

contrasted 是动词 contrast 的过去式。contrast 由前缀 con-（表示"共同"）和词根 -trast（来自拉丁语，意为"站立"）组成，字面意思是"并立对照"。在句中表示"形成鲜明对比"的意思。