J. B. Priestley uses dramatic devices and dramatic irony to signal characters and introduce the inspector. For example, the house is pink and intimate while they are celebrating the engagement, but when the sharp ring of a door bell is heard, the lighting changes to a brighter and harder colour. Some believe that it represents an interrogation room due to the bright lights that are shining on the Birlings as the inspector comes in and picks the story out of them bit by bit. Dramatic irony is used throughout the play to create prejudice between Mr. Birling and the audience. 