The blanking color is used to paint blanked pixels in images. By de-
fault at startup this color is white. This can be customized with
LUT /BLANK Color
where the color is one of the supported pen colors (type LUT /BLANK ?
for the complete list). The 2 most relevant values are BACKGROUND and
FOREGROUND which translate as WHITE or BLACK depending on the device
color.
For a custom blanking color, use command LUT LUT (see subtopic for de-
tails).