Thank you for writing.
The issue with the RadTrackBar back color is a known issue, which we will address in one of our future releases. Until then you can set the back color of the RadTrackBar through the following code:
TrackBarPrimitive primitive =
primitive.BackColor = Color.Transparent;
I hope this will help you. If you need further assistance, I would be glad to provide it.
the Telerik team
Q2’11 SP1 of RadControls for WinForms is available for download (see what's new); also available is the Q3'11 Roadmap for Telerik Windows Forms controls.