Though the story deals with universal issues, its characters are very much defined by their geographic location and their location in history. They are living in Mississippi in the 60 years following the Civil War. For the most part, this location defines the characters negatively, focusing on the difficulty the South faced in transitioning to a completely new way of life.
Emily will be forever defined by her bizarre habits, one of which seems to be cozying up to her dead lover's corpse. She is most of all defined by her reclusively. Which is almost like no definition at all, since we can't follow her into the house. Tobe is defined by the fact that he stays with Miss Emily there in the house.
For Tobe, Emily is a habit. She's a habit for the town, too, often in a not nice way. The different generations represented in the story each has a slightly different way of dealing with Miss Emily, but, as shown be the repeated reference to her as "an idol" they all treat her more or less like an object. We can make it a habit to try to see beyond Emily as an object, and into Emily as a human.
Hair color defines Tobe and Miss Emily as elderly people while also showing the passage of time in the story. As a black man in the South in those times, Tobe's appearance defines him in terms of his available options, in his status as a servant, and in how he is looked at by the townspeople. Like Emily's eventual obesity, Tobe's skin color isolates him from the world at large.
Something about Emily's physical appearance (and this is another factor in her isolation) is also divine. She's described as looking like "an angel" after her father's death, just before she hooks up with Homer. She's also described twice as looking like "an idol." This blends weirdly with the idea we have of her as murderer and insane person.
Tobe, the townspeople, and Emily can be seen to represent three layers of social status. Least wealthy, wealthier, and wealthiest, respectively. But over time, due in large part to the Civil War and Emancipation, these clear distinctions get all jumbled up, and the characters don't know quite how to handle it. They are defined by both the past and present social statuses, which overlap and interweave painfully. For example, Tobe is no longer a slave, but still a servant. Emily is no longer wealthy, but still a Grierson, which means she has to act like a lady at all costs.