The clue “King Duncan’s death at the hand of Macbeth comprises the play’s only historical truth” tells you that the version of events related in Macbeth was not very accurate. Does anachronistic mean inaccurate? No; cross it out. What about effusive? No. In contrast, embellished works well, but prosaic and serpentine do not. Finally, colored—which, like embellished, means misrepresented or distorted—fits the blank nicely.