In this case translator should know historical fact.In civil war, south army dress in gray ,so were called Gray, while noth army dress in blue, so were called Blue.

• 贝里维尔市内及其周围的家庭都已离开自己的家园或农场，穿灰色服装的南方军和穿蓝色服装的北方军仍在这个河谷激战。