I'm looking for any physical characteristics that may represent something or what she as a whole may represent or stand for in the story.
Lucie is the "golden-haired doll" who charms just about everyone she meets with her beauty. She’s got yellow hair, as you’ve probably guessed. More interestingly, however, Dickens uses her hair color as an image that binds her family together. She becomes the "golden thread" that unites her father with his present, not allowing him to dwell too much in the horrors of the past.....Lucie unites Carton to Darnay, Dr. Manette to Darnay, and Mr. Lorry to the family in general. Lucie becomes the reason that Charles escapes the grasp of the Republic’s "justice."
http://www.shmoop.com/tale-of-two-cities/golden-thread-symbol.html
