ChartFont.Background (Word)

Returns or sets the type of background for text used in charts. Read/write Variant that is set to one of the constants of XlBackground. Possible return values are xlBackgroundAutomatic - Word controls the background, xlBackgroundOpaque - An opaque background, xlBackgroundTransparent - A transparent background.

With ActiveDocument.InlineShapes(1) 
 If .HasChart Then 
 With .Chart 
 .HasTitle = True 
 .ChartTitle.Text = "Rainfall Totals by Month" 
 With .ChartTitle.Font 
 .Size = 10 
 .Background = xlBackgroundTransparent 
 End With 
 End With 
 End If 
End With