// Sets the back color to pale green
BackColorAll = Color.PaleGreen;

// Sets the back color to the default color set in the chart properties dialog window
BackColorAll = Color.Empty;

// Sets the back color to pink when the closing price is less than the 20 period SMA
// and to lime green when above (see image below)
BackColorAll = SMA(20)[0] >= Close[0] ? Color.Pink : Color.PaleGreen;