Authors write about various regions to depict unique characteristics about the areas. This "color" includes

The answer that best completes the statement above is this: stylistic sketches of local performances. Basically, this is what is being referred to the "color" in which authors write regarding various regions in order to convey unique characteristics of the region. With the use of stylistic sketches of local performances, the uniqueness of each region is being presented very well making it clearer for the readers.