New Post: Caption background color ignored

I am trying to place colored text on a black caption area. However, it seems no matter what I set the background color it doesn't change. The caption area is always remains white. Any ideas what is going on?
Using Any-Cpu version 7.0.0.0018 in VS2013

                'Add Timestamp Caption

                    Dim CaptionbgColor = New MagickColor("#000000") 'Color for the caption background color doesn't seem to take
                    Dim CaptionfontFamily = "Arial-Italic"

                    Using timestampImage = New MagickImage(CaptionbgColor, 352, 14)
                        timestampImage.FillColor = New MagickColor("#9900FF") '__This works__ and changes the font color
                        timestampImage.Font = CaptionfontFamily
                        timestampImage.FontPointsize = 12
                        timestampImage.Read("caption:As of " + Now.ToString)

                        'TimestampImage
                        image.Composite(timestampImage, Gravity.North, CompositeOperator.Over)
                        'Save the result
                        image.Write(myFilesTempOutputDirectory + "imagePostOverlayCaption.jpg")
                    End Using