Runtime created Column Group in Header for some columns only. The columns do not have any Column Group it show black strip over it. How to get fill that back color.

[Laxman]

Hi Support Team,

I am using following code to create column Group at run time .
To create a new group programmatically use :
GridViewColumnGroup columnGroup = new GridViewColumnGroup();
columnGroup.Name = "XXXXXX"; // replace the XXXX with a name of your choice...
To tell a column it belongs to a given group use : 
this.RadGridView1.Columns[0].ColumnGroupName = "XXXXXXX";
To add a programmatically created group to RadGridView use :
this.RadGridView1.ColumnGroups.Add(columnGroup);
I am creating grid columns at run time based on business requirement and for some columns which are constant and added at design time  is also having column group strip with Black color which user does not like so I want to get rid of that color and make its color as Rad Grid backgroud color. Screen shot of the issue has been attached with this thread.
Please help me to resolve this issue. Please have a look in the attachment. If you do not understand please let me know so I can post code as well. It happens in both the versions which are following:

Telerik\2011\Q3\WPF\2011.3.1220
Telerik\2012\Q2\WPF\2012.2.725



Thanks
Laxman.