After I finished the black and white under-painting, I filled the canvas with transparent layer of magenta. Now I've started to block in color. The color on top combines with the magenta underneath, to give it a cohesive feel. It helps the all the colors to fit in, and not stick out like a sore thumb. (now you see why I paint, and not write literature ;)
I've only worked on the color, for about an hour. I have many hours left, before I can declare this finished. So all I can do, move on and sally forth. Will post again soon.