In Visual Studio 2010 Tabs Studio uses separate default style. As in .NET 4.0 OuterGlowBitmapEffect is no longer supported, I changed its usage to DropShadowEffect. DropShadowEffect is less visible, but at the moment I don’t know what else to use. Notice less red over close tab button and less white over selected tab content in Visual Studio 2010:
Default style for Visual Studio 2010 also sets transparent tabs background.