This area of the 3D pane of Motion Preferences lets you modify settings for the grid that
appears in the Motion 3D workspace.
3D Grid Spacing:
Specifies the spacing between grid lines, in pixels.
Primary Grid Color:
Lets you set the color of the main grid lines. The main grid lines
appear slightly heavier than the secondary grid lines.
Secondary Grid Color:
Lets you set the color of the secondary grid lines (the lines that
appear within the main grid lines).