Why was the girl in red in Schindlers list?

Watched it again last night.Great movie,powerful performances,thought provoking.However, the scene where the nazis liquidate the ghetto, where a little girl is seen wandering aimlessly through the bedlam in the streets.Wondered was their ever an explanation given by Spielberg for why she was seen dressed in a red coat?Or was this left to the interpretation of the audience? I always viewed it through the eyes of Schindler,as he apparently is the only person who sees the girl in this light.Interested to hear whether any official interpretation was ever given & if not, what would your view on this be?