when you disable the MenuItem in this code:
<MenuItem IsEnabled="False">
<MenuItem.Header>
<StackPanel Orientation="Horizontal">
<TextBlock Text="{x:Static properties:Resources.SEARCH_FOR_DAYS}" />
<TextBlock Text="{x:Static properties:Resources.ELLIPSES}" />
</StackPanel>
</MenuItem.Header>
</MenuItem>
the text doesn't become gray.
But if you make the same thing in this other code:
<MenuItem IsEnabled="False">
<MenuItem.Header>
<StackPanel Orientation="Horizontal">
<Label Padding="0" Content="{x:Static properties:Resources.SEARCH_FOR_DAYS}" />
<Label Padding="0" Content="{x:Static properties:Resources.ELLIPSES}" />
</StackPanel>
</MenuItem.Header>
</MenuItem>
Enable and disable works as expected on the color of the text