After carefully looking at the attached screenshot, it seems that you want to change the background of the ToolWindow popup. Note that when you show an auto-hidden ToolWindow, RadDock displays a RadForm. You can apply the same BackColor as the main form because the controls transparency is a common problem in the whole WinForms. You can find useful information on this topic on the following links:
Private Sub AutoHideWindowDisplayed(sender As Object, e As DockWindowEventArgs)
Dim hw As HostWindow = TryCast(e.DockWindow, HostWindow)
Dim popup As AutoHidePopup = TryCast(hw.ParentForm, AutoHidePopup)
popup.ToolStrip.BackColor = Me.BackColor
I hope this information helps. Should you have further questions, I would be glad to help.
Do you want to have your say when we set our development plans?
Do you want to know when a feature you care about is added or when a bug fixed?
Telerik Feedback Portal
and vote to affect the priority of the items