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Commercial classes are also characterized by their seed coat color. Seed coat color is defined by the pigmentation underlying the testa and may be distributed throughout the testa as a solid or mottled pattern. The appearance will range from glossy (shiny) to a matte (dull) finish. The glossy finish is associated with the presence of a lipid layer on the surface of the testa. The P locus is known as the ground factor for all seed coat color genotypes (Bassett 2007).

Pigments found within the seed coat are typically phenolic compounds (e.g., phenolic acids, condensed polyphenols, or tannins and flavonoids, particularly anthocyanins) that impart a distinctive color and are reactive to soak water chemistry and pH (Singh et al. 2017). The general descriptive classification of phenolic compounds is presented in ssss1. This broad class of phenolic compounds influences the reactivity of various cross‐linking reactions between proteins and thus is associated with decreased water transmission rates and water‐holding capacity of the seed. These polyphenolic compounds, mainly tannins found in the seed coat, are present in black, red, and brown beans and produce desirable agronomic effects (abiotic stress tolerance and the prevention of in‐pod sprouting). Further, these compounds are potentially associated with a wide range of plant biochemical and metabolic functions including (1) resistance to disease, (2) wound‐healing response, and (3) insect and bird resistance.