// Sets the chart panel back color to pale green
BackColor = Color.PaleGreen;

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

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