The Speakers
The Speakers are Jewish prisoners in a Nazi death camp. They are also speaking with the voice of Paul Celan, because he experienced exactly what they are experiencing. Each stanza appears to be voiced by a different speaker. Each share a similarity in the way they have become almost immune to their dehumanization; they have come to view themselves in the same way that they are viewed by their Nazi guard. They do not think independently anymore and consider themselves an "us" rather than an "I".
Their days are identical and difficult to discern from each other. They dig graves, they hear the beautiful music played by their fellow prisoners, they have come to know much about the character of the man who guards them, they watch the murder of their friends and they know that their own murder is just as likely. They are past the point of fear (their situation is far more frightening to us reading the poem than it is to them as the subjects of it) and almost long for death as the inevitable. They believe it would be more comfortable than the life they are living.
The Man
The man is a Nazi guard who personifies the Germans and their belief in Hitler's vision for the Aryan nation. He is blonde haired and blue eyed, which on the face of it sounds pleasant but to the prisoners is a terrifying symbol of what they are not and what one has to be in order to survive in the German nation. He is an educated man capable of deep appreciation of literature and music, and also capable of the most heinous acts of brutality and murder. His life is one of extremes; he appreciates beauty and creates something that is unimaginably ugly. He writes every night and contemplates the beauty of the stars. From his house he can see nothing but beauty and hope. He is also completely oblivious to the ugliness of what is around him, because to him it is its own kind of beauty that he is helping to create. His adoration of "Marguerite" shows that he is a follower of Hitler's doctrines and that he is not just participating in these murderous acts because he is scared not to; he actually enjoys it.
Marguerite
Marguerite is a blue eyed, blonde haired golden girl who is a symbol of the perfect German. She is based loosely on a character in Goethe's "Faust". She is adored by the guard because of what she represents.
Shulamith
Shulamith is ashen haired rather than blonde; although beautiful, she is the opposite of Marguerite and therefore the opposite of what is required to be a part of the German nation. Her ashen hair is a symbol of the burning of the Jewish prisoners and the fact that their race and culture are being removed from Germany.