Local color, as a literary term, refers to depictions of life and character in a particular locality. The customs of the people, their speech, their peculiar way of looking at things is presented to the reader, often in a slightly sentimentalized or nostalgic form. Dickens' Mr. Micawber and the Artful Dodger are local figures, and their environments are local color settings. Bret Harte is probably the best-known American practitioner of the genre.
Comic relief is a familiar term which needs little discussion. An author will seek to relieve the intensity of a serious plot line by inserting comic characters or situations; these entertaining diversions help keep the reader's interest lively and balance out the fictional picture of our half-tragic, half-comic world. Probably the most famous example of the use of comic relief in English literature is the knocking at the gate in Macbeth, where the sight of the drunken porter relaxes the audience after the murder of Duncan.
Eliot uses both these devices in Adam Bede. In a sense, most of the novel is local color; the settings and the speech of the characters obviously belong to a specific time and place. But certain characters function almost entirely as local color figures: Wiry Ben, for example, or Chad's Bess, or Mr. Craig. These people are part of the novel's background; they provide a concrete milieu in which the central action of the story takes place. Mr. Poyser is a typical (though unusually skilled) Warwickshire farmer; Wiry Ben exemplifies the typical attitudes of the Warwickshire town laborer of his day.
Eliot gives a lot of attention to the habits and customs of the local people. Most of Chapters 6 and 18, for example, describe what ordinary people did and said on ordinary days in the Warwickshire countryside in 1800. The operation of the Hall Farm and the description of Sunday morning churchgoing are presented not because they are relevant to the novel's conflict but because they help make up the picture of a realistic, functioning, physical world. Parts of Book III (especially Chapter 25 on the games at Arthur's birthday party) show how people celebrated an important event; Chapter 53 describes the local ritual of the harvest supper.
The sections of the novel which concentrate on developing local color serve other purposes as well. Book III, as noted in the commentaries, is the calm before the storm; Eliot builds up suspense by talking of minor matters while delaying the explosion of the inevitable conflict. The long descriptions in Chapter 18 put Thias Bede's death in context; if treated as anything other than a "typical" event, his funeral would assume too much importance in the story, thus diverting attention from Adam's real soul-crisis at Hetty's trial. And Chapter 53 wrings the last bit of suspense from the plot by "marking time" while Dinah thinks over Adam's proposal.
They also serve, of course, to provide comic relief, Eliot normally places her local color descriptions so as to perform this secondary function as well. It is no accident that the relatively light-hearted Book III comes after the lines of conflict in the novel have been somewhat grimly drawn and before Adam's fight with Arthur, or that Chapter 32, in which Mrs. Poyser routs Squire Donnithorne, interrupts the development of Hetty's tragedy.
Thus local color and comic relief work hand in hand in Adam Bede. Eliot, determined to write a realistic novel about common, everyday people, delves into her memories of her Warwickshire childhood and creates a specific, concrete world peopled with generally plausible figures. She projects it back in time past the date of her own birth and perhaps sentimentalizes it a little; one wonders whether rural folk in 1800 were really as charming as she presents them. And, though she is writing a very serious book, Eliot does not forget (as she tended to do in later works) that one function of the novelist is to entertain. So she provides us with something to laugh at with her Bartle Massey and Wiry Ben and hits a nostalgic note with the harvest supper. But most of all, as local color and comic relief, she gives us the inimitable Mrs. Poyser. Perhaps no tenant's wife in 1800 would really tell her aristocratic landlord "you've got Old Harry to your friend." But then again perhaps she would, and it is both educational and amusing to hear Mrs. Poyser "have her say out."