Please refer to the modified sample
The docking window on the left hand side of the form is a GroupBar control. The GroupBar control has 2 GroupBarItems in it. The GroupBarItem1 has a ListBox in it and setting its BackColor will set the GroupBarItem''s client area to a desired color (crimson here). Similarly, you could set the BackColor property for the panel hosted in the GroupBarItem2''s client area.
When a control (the GroupBar here) is docked, it is hosted within a DockHost and a rectangular caption bar is attached on top. Like I mentioned earlier, please handle the DoockingManager''s ProvideGraphicsItems event to customize the BackColor/ForeColor of the caption.
Please refer to the screenshot
attached which shows how this sample looks at runtime here. Let me know if this meets your requirements. If not, mention the areas in the screenshot that you need paint with a custom color. We appreciate your cooperation.