You can go to override graphics in view (by category) and ensure that the category is not overridden.
That is the setting of the wall itself, how it is displayed in the detail level ‘coarse’ mode, in graphics display Consistent Colors You can change the color of the wall for ‘coarse’ detail level, See the picture below.
or change the detail level to medium or fine
In the materials browser search for a material called ‘Poche’ change the color to grey
You can also access it by going to the properties of the 3d view. Open the type properties and change the coarse poche material to grey