Could you attach a solution file (a sample) that could be tested on our side ?
As for the background color that is not grayed out, you can now set any color to the WindowContainer when a modal window is open in the WindowContainer, with the ModalBackgroundBrush property. The "ClickOnce app" available on https://wpftoolkit.codeplex.com/ shows it in the "WindowContainer sample" of the application.
The old version of the ChildWindow was setting a background gray to it's parent, which is not very object oriented. Now the WindowContainer contains ChildWindows and set its background color when modal windows are open. This is why the WindowContainer should be placed over background controls that should be blocked while a modal window is opened in the WindowContainer.
In the meantime, the old ChildWindow is still working, but is deprecated.
As for the background color that is not grayed out, you can now set any color to the WindowContainer when a modal window is open in the WindowContainer, with the ModalBackgroundBrush property. The "ClickOnce app" available on https://wpftoolkit.codeplex.com/ shows it in the "WindowContainer sample" of the application.
The old version of the ChildWindow was setting a background gray to it's parent, which is not very object oriented. Now the WindowContainer contains ChildWindows and set its background color when modal windows are open. This is why the WindowContainer should be placed over background controls that should be blocked while a modal window is opened in the WindowContainer.
In the meantime, the old ChildWindow is still working, but is deprecated.