Red and Black
Michael Henchard's face is often described as a combination of red and black. Weird as that sounds, we're probably not supposed to imagine that he looks like Darth Maul from Star Wars. Although Henchard is racially white, he's very tan, and his work in the outdoors has turned his skin ruddy and red. Folks used to describe being very suntanned as being almost "blackened" by the sun.
Henchard also can't hide his emotions, and his blood is always rushing to his face when he's angry or upset ("Henchard looked at him with a face stern and red" [15.34]). This also helps account for the "redness" of his face.
What else could the red and black coloring suggest? Let's check out another example:
Elizabeth-Jane now entered, and stood before the master of the premises. His dark pupils – which always seemed to have a red spark of light in them, though this could hardly be a physical fact – turned indifferently round under his dark brows until they rested on her figure. (10.10)
This description of Henchard makes him sound pretty scary. Dark eyes with a "red spark" in them sounds almost demonic. Is the narrator suggesting that Henchard should be associated with the devil? Not in any literal way, but perhaps this description is meant to imply that Henchard has very little control over his own metaphorical inner demons – his bad temper and his pride.
Bridges often have symbolic weight when they appear in literature. There are two bridges in The Mayor of Casterbridge, one brick and one stone. Both bridges attract people who feel like "failures" (32.4). Sometimes these people try to throw themselves into the water below, but mostly they just like to lean against the rail, stare down at the water, and feel dejected.
Why would a bridge be an appropriate place for people who feel like "failures" to congregate? What might the bridge symbolize?
Bridges represent connection. They literally connect different places, and metaphorically they suggest the connection of ideas. So standing on a bridge might suggest that a person is stuck at some "in-between" stage – between jobs, between relationships, or unable to make a decision. Lingering on a bridge could symbolize stagnation: the person is standing still while the water below and the passersby on the bridge keep moving.
The Five Guineas
This is the amount of money Henchard received from the sailor in exchange for his wife, Susan. A guinea is a unit of British currency (now no longer used) equal to one British pound plus one shilling. It was a lot of money back in the late 19th century. So five guineas was a whole lot of money for a poor man back in the day.
Michael Henchard is very into symbols. We're told in the second chapter that there is "something fetichistic in this man's beliefs" (2.7). So he actually turns the five guineas into a symbol himself by making a big show of giving Susan five guineas when they're reunited. He is symbolically "buying her back." ("The amount was significant; it may tacitly have told her that he bought her back again" [10.43].)
The Casterbridge Ring
The "Ring" is an old Roman amphitheater (like a smaller version of the Colosseum in Rome) just outside Casterbridge. The narrator tells us something about the history of the place: during Roman times, it was used for public entertainment. In later years, it was used for public executions. More recently, it had been used as a place to meet for private duels. The circular seating screens the interior from the road, so no one passing by can see what's going on inside.
The Ring is an important setting in the novel for two important scenes: Henchard's first reunion with Susan and his meeting with Lucetta. During the second, the narrator even remarks on the similarity between the two scenes. The Ring's ancient history and the fact that scenes tend to repeat themselves there suggest that the Ring might be an emblem for the way the past comes back to haunt the present. Characters cannot escape their history.