Maggie’s "dark" coloring (her hair, her skin, and her eyes) might seem like weird symbols. They are certainly mentioned enough to qualify them as motifs, or repeating themes and images. We start hearing about Maggie’s dark skin and crazy hair from the very first chapter. Notably, Maggie’s "dark" looks are frequently referred to negatively by her relatives. Here Aunt Pullet comments on Maggie’s looks:
I think the gell has too much hair. I’d have it thinned and cut shorter, sister, if I was you: it isn’t good for her health. It’s that as makes her skin so brown, I shouldn’t wonder. (1.7.45)
Aunt Pullet see’s Maggie’s hair as a "problem" to be solved. Maggie’s dark hair and skin help to set her apart from the rest of the extended Dodson clan and, as a result, Maggie’s physical appearance helps to reinforce the ways she differs from her family in terms of intellect, emotions, ideas, and behavior.
Maggie’s dark hair and skin also have some racial connotations, or meanings. In this time period, a lot of English people thought that white people were superior, and the whiter your skin was, the better. White skin was also related to class prejudices. Women who had money and didn’t have to work could remain indoors and avoid getting a tan. So white skin was a marker of money and status as well. Maggie’s darker skin is unsettling for her family, since she is part of a middle class family. Her skin and hair imply that she is somehow wild or poor or "savage." Maggie herself even makes note of this when she observes that her family often compares her to the gypsies, a group that society looked down upon.
So Maggie’s hair and skin help to set her apart and also prejudice a lot of people against her. Her eyes also add to her uncanny and striking appearance. Maggie’s eyes are frequently described as somehow hypnotic. Stephen is always wanting Maggie to look at him; he’s almost obsessed with her eyes. And it is no coincidence that Lucy considers Maggie as somehow supernatural, describing how Maggie uses "witchcraft" and has a "general uncanniness" (6.3.28).
Going off her odd physical features, Maggie does not really seem to belong in the world of St. Ogg’s, even though she feels quite passionately about her home. Maggie’s "dark" features help to represent the ways in which her character has trouble dealing with her competing emotions and the ways in which her character struggles to fit into her surroundings.