SetDrawPlotAreaBackground — Enables drawing of a plot area background color
$plot->SetDrawPlotAreaBackground($dpab)
SetDrawPlotAreaBackground enables or disables drawing
of a solid fill color behind the plot area (the area inside the axes,
typically). By default, no plot area background color is used, which
results in the overall image background color applying to the plot area.
$dpabIf True, draw the plot area background color. If False, ignore the plot area background color.
The actual color which will be drawn in the plot area background is set with SetPlotBgColor.
Plot area background color is ignored if a plot area background image was set with SetPlotAreaBgImage.