I thought I'd put together some mixes with French Ultramarine. They're kind of in the spirit of my previous mixing exercises, but here I focus on one pigment. As one can see, I have accumulated an awful lot of paints. Perhaps with a few more of these studies I might cull that pile of paint down a bit.
I've also been thinking about value... Desaturating the chart helps me separate hue from value. I'll have to try this with my sketches too.