Mussini Burnt Sienna.
Burnt Sienna is dark transparent Orange.
It is permanent and always on my 19 color acrylic palette.
BURNT SIENNA, MIX IT WITH COBALT BLUE TO GET ALL BROWNS,
wash it over blue to warm it up while keeping all the details.
Burnt Sienna is a dark translucent or transparent pigment, depending on the supply.
I have an old 1980 oil-color tube that glimmers a cadmium orange hue back to me.
An orange-to-brown natural pigment PBr:7 with a red-side top-tone
(as shown above) and an orange-side under-tone.

Burnt Sienna is not dual-toned as the transparent dual-toned
Indian yellow-to-brown pigment PY:150 - PY150 and the Indian yellow-to-orange pigment PY:153 - PY153,
or as opaque as the red's (half-way-to-brown-in-the-gradient) Venetian red oxide.