They eat beans mostly, this old yellow pair. (line 1)
Brooks starts her poem off by signaling that this couple is "yellow," suggesting that they're either black (with fair skin) or Asian. Placing such a description in the first line makes it one of the framing points of the entire poem.
As they lean over the beans in their rented back room (line 11)
It's not explicit, but this couple's financial circumstances are in some ways directly related to their race. After all, "equality" wasn't exactly a perfect system back in the '60s (or even today). Check out what we have to say in "Setting" for more discussion on this!