Reread the very last sentence of this chapter. How are the newcomers paralleled with "Tom" and "Chambers"?

Certainly these two represent Tom and Chambers,

"Then entered the twins -- the handsomest, the best dressed, the most distinguished-looking pair of young fellows the West had ever seen. One was a little fairer than the other, but otherwise they were exact duplicates."

The colour factor plays heavily into the context of the town and, of course, the dynamic between Tom and Chambers.