Just a few brief notes:
The blue-black colors in kernels (in a single-cell layer just under the
clear hull, or pericarp) are caused by the same pigments that cause
flower colors like those in bachelor buttons or red roses. The colors
are deeper and blue-black in part because of the quantity of pigment and
in part because the pigments are associated with proteins in the kernels
that change their colors.
The red seed colors in the same layer of the kernels are like those in
geraniums and strawberries.
Lighter and darker colors are the result of quantity changes, and of
changes in other contents of the kernels.
The brick-red colors, and the stripes in calico-striped ears, are caused
by similar pigments, which have oxidized into products like those in
autumn leaves.
Yellow kernels are pigmented by carotenoids, precursors of vitamin A.
White kernels lack these pigments.
The actual "meaning" of the pigments, in the sense of their function, is
subject to conjecture. A number of studies have suggested, some more
convincingly than others, that these pigments (or colorless relatives
synthesized by the same processes) have a role in insect resistance or
fungal resistance.
I hope this is helpful.
Ed Coe
