The second ring of color is the tints of each color, this is white added to each color. The third ring of color is a layer of black pencil added to each color to create the shade. The inner ring of color is the mixture of each complementary which are directly across from each other on the color wheel. Mixing complementary colors creates colorful dark values.
The initial drawing stage took quite a bit of time as I wanted to draw in each highlighted vein. I am striving for abstraction and movement in the veins and the overall piece.