the color of the background, "black" and foreground
"white" lines of the box.
nx, ny
number of cells of the grid in x or y direction. When NULL,
as per default, the grid aligns with the tick marks on the
corresponding default axis (i.e., tick marks as computed by axTicks).
...
additional arguments passed to the grid() function.
Details
decor is equivalent to hgrid() followed by boxL().