going slightly mad with LODs

Hi boys and girls,
I would like to change the materials of my different LODS for a mesh.
All the tutorials show it’s easy to do. But, on my system (ver. 4.23.1) the picker for material in LODS is grey, and I can’t do anything to turn it white (which would allow me to f… change the material).
I’m presently crying waiting for your help.