Bill Tindall, E.Tn.
All artist pigment burnt umber is not the same shade. Some is a yellowish brown while others reddish brown. To keep some of the reds seen in fresh exposed walnut I search for a tube of artist pigment that has the reddish cast. Art stores have been accommodating to let me squeeze a tiny bit of pigment onto something white.
Burnt umber pigment is a mineral pigment probably composed of iron, and maybe some manganese, oxide. I suppose "burnt" umber is this mineral that has been heated. Heating will make red ferric oxide more or less depending on how much heating. Other combinations of iron, water and manganese will yield yellow or brown or black. Add manganese and the stuff becomes darker, and with enough manganese, black.
These pigments are dug from the earth with the variability one might expect from the various combinations of mineral oxides with location. The result are pigments that span red to yellow to brown and dark brown, further altered by heating.
The advantage of using a mineral pigment is that they do not fade or change colors at all. What you wind up with after staining is what you will have, for the most part, years later. I like that property. None of my walnut furniture has bleached to the light yellow -brown walnut will become without some added coloring, either from stain or finish.