I found my burnt umber pigments and mulled up a couple of tubes. From left to right: Burnt Umber Reddish, Burnt Umber Cyprian Dark Brown, Raw Umber Cyprus Medium. Here you can see the wonderful range from red to green. Isn't this amazing from the same basic earth pigment?
I can imagine using the Cyprian Dark Brown for a grisaille underpainting to set the tones and then applying light glazes of transparent pigments for color.
By the way, the burnt really stands for the heat treating of the umber to warm the color and in some cases increase the transparency.