You can remove any material overrides you created on a render layer and revert back to the material shader used in the master layer.
To remove a material override from an object in a render layer: method 1
the
object and select Remove Material Override. A
list of material overrides for the selected layer appears in the menu.

To remove a material override from an object in a render layer: method 2
the
material swatch and select Remove Material Override From.
The menu lists all objects in the layer that use the material override.

If a material is currently
not used as a material override, the menu displays "There are no
objects with override" when you
a material swatch
and select Remove Material Override From.
