Even though I have begun color at this stage, I am still thinking of it as under-painting. In fact, the more I develop as a painter, the more I find that most of my time spent on a painting is "underpainting" - preparing the bed of values and hues the final painting will lay over.
So here I am mixing my values with colored pigment instead of just grey. I'm also just starting to warm up the colors of the shell, message paper and tissue.
Finally, I am adding a new level of refinement and detail as I make my first pass of color.