As stated in the C7 Operation manual, p. 705 (‘Customizing’ chapter) :
The work areas in Cubase are those places where the actual data are displayed such
as the Project window event display. In these areas, there are items such as vertical
and horizontal grid lines that can be altered in intensity by the controls found on this
This page no longer exists (at least, in Cubase 7.0.1) and is mandatory to fix the different vertical grid levels intensity, as well as the horizontal one. Hope that this will be fixed in the next update.