Another two-color study, this time using Burnt Sienna instead of Burnt Umber, along with the Ultramarine Blue.  As an aside, looking up lists of “warm” and “cool” colors, the umber and ultramarine are considered “warm” by some.  Beats me, as they sure look icy together.  Here, the Burnt Sienna alone or diluted is warm in cast, but moves to dark and cold (in my eye) when combined with the Ultramarine Blue.