Selecting GreyScale from the Plugins menu
causes all materials and textures in the model to change into
the greyscale color.
The textures themselves are not removed
from the model, but only re-colored.
Front Face Mode
Selecting the Front Face option makes all materials and textures
match the currently selected Fron face color as seen in
the Edit Styles dialog.
This mode is similar
to the Monochrome mode in SketchUp except that textures will remain.
Reverting a Single Color
By right-clicking in either GreyScale or Front Face mode, individual
colors may be reverted to their original values for emphasis.
Files may be saved in either GreyScale or FrontFace mode
with no problem. When the file is opened again, it will remain
in the same mode as when saved, so check the Plugins menu to see
which state the model is in, and revert it if desired.