Do I have to do something special to the Label control from the Silverlight toolkit to get the current themed applied?
When looking at the Theme Browser on the demo page it appears as though labels should be turning white in the expression dark theme, but it's staying black for me.
it works fine for me. You might have an implicit or explicit Label style that overwrites it.
Edit:
<Grid x:Name="LayoutRoot">
<toolkit:ExpressionDarkTheme>
<Grid>
<sdk:Label Content="label" HorizontalAlignment="Center" VerticalAlignment="Center"/>
</Grid>
</toolkit:ExpressionDarkTheme>
</Grid>