I have colored the shadows with my favourite purple crayon - Harold would be proud.
(Faber Castell Color Pencil #249 - Mauve...in case you're taking notes. )
I can now start to see the patterns of light and shade that draw me through the composition (no pun intended). With the darkest part of the picture on the top and all the light at the bottom, I think it will be an interesting challenge not to make the picture feel top heavy.