Material is grayed out and can not be applied, assigned or attached.Why a material is grayed out?
Material name exists in another loaded Palette.If a material with the same name exists in another loaded palette (PAL), it will only allow the use of one of the materials, the rest will be disabled (grayed out).The tools on the Apply Material dialog will be grayed out. The material editor will also display a "grey sphere" material icon as opposed to the normal "blue sphere" icon.