Throughout the play Blanche dresses in white; a symbol of the virginal image she wishes to portray but which is so far from the truth. In Scene 5 when she is talking about starsigns to Stanley and tells him she is a Virgo he asks, "What's Virgo?", to which she replies, ""Virgo is the Virgin" and he laughs at her. She is hiding secrets and memories of such significance they hurt her daily. Williams shows the audience this by the recurrent 'Varsouviana' tune, her alcohol abuse and her frequent bathing. The bathing is said to be for her nerves but in reality she is trying to rid herself of the guilt she feels for her past, most notably for her part in the suicide of her husband. Their whole relationship was based upon one huge illusion and like Blanche, it was lies that led to his demise.
Her clothes mask a whole array of issues. They conceal her insecurities as she plays dress-up as a little girl does, creating new charcters for different situations; southern belle, the teacher, the virgin and on rare occasions, her true self. Stanley maliciously teases Blanche when she is at her weakest; in Scene 10 he mocks her by calling her rhinestone tiara, diamond and suggesting he wasnt aware of its lack of value. By this point in the play she has fooled herself so many times she cannot distinguish between reality and fantasy. In some ways I see Blanche as being innocent in that she is constantly longing for a fairytale ending, for the man who will love her and treat her as she should be treated but her approach is based upon lies and it is these lies that push Mitch away. By reducing her concerns to her appearance alone she gets rid of the need to worry about her current situation and the actions of her past. Her fear of growing old and becoming unlovable is so severe she refuses to be seen in light but this is more a symbol of being seen for who she really is than fear of being ugly.
Blanche uses her alcohol abuse to conceal her problems but the abuse in itself is another problem she tries desperately to delude people about. She says things like, "Now don't get worried, you're sister hasn't turned into a drunkard...". She hides the bottle when Mitch comes over but she fools noone. Brick in 'Cat on a Hot Tin Roof uses alcohol as a way to feel closer to Skipper who's alcohol and drug abuse destroyed him after Margaret confronted him about his relationship with Brick, just as Blanche calling the boy when she was 16 "disgusting" . Williams also fell into drug and alcohol addiction, perhaps because he never got over the death of his first love, Kip.
The use of lighting is critical to show Blanche's hatred of being exposed. To be seen would leave her vulnerable to scrutiny, something she could not stand ('I won't be looked at in this merciless glare'). Her white clothes are said to "suggest a moth"; she is delicate and drawn to the light but in doing so she is doomed to die. Originally Williams was going to call the play 'The Passion of a Moth'. In Scene 1 she says "Daylight never exposed so total a ruin!". She doesn't just mean her fading looks but that she as a whole has become a ruin. The use of colours is very important. There are lots of references to white which shows the purity Blanche wishes to possess. As she fantasies about her death in Scene 11 she imagines she will "be sewn up in a clean white sack and dropped overboard...into an ocean as blue as [her] first lover's eyes!", a very clinical and idealistic view of death, so far from what is likely to be the reality. The lantern she buys to cover the light is brutally ripped off by Mitch just before she tells him she wants magic instead of realism and that she "tell[s] what out to be the truth." This is a huge violation of Blanche surpased only by Stanley raping her in Scene 10. Her ideals are torn from her, she is exposed in the most degrading and distressing way and it is this savage act of reality that pushes her irretrievably into madness and illusion.
Blanche may live in a world of illusions but the world of reality is so depressing that it is a survival method that kept her safe and sane for many years before it eventually lead to downfall. The interjections of realism are the things which destroy her. She seeks a make-believe world which, although not perfect, is a far more pleasing existence than reality.