I am trying to assign a material to the smoke simulation I have created. For creating the simulation I added a cube, and I click object->quick effect->quick Smoke. Then I have setted the smoke parameters and started the simulation. I can't assign any material to the smoke domain, or to the smoke itself, it remains purple in color. Also adding a principled volume in "Shader Editor" has no effect at all on the purple color of the volume. I attach 2 images to show what I am trying to explain.
Your shader assignment looks correct to me.
I suspect the purple color does not come from the smoke shader itself, but rather from a missing texture somewhere else like the world shader for example. Could you check that ?
Otherwise, a simple test could be to open a new fresh scene, do a quicksmoke on the default cube, setup the domain shader ans see how it goes. If it still fails, then maybe it's a bug.